The present invention relates to improved continuous multifilament nylon apparel yarns and more particularly relates to a warp-draw process for making nylon flat yarns and improved yarn products made thereby. Nylon flat yarns are used in a variety of woven and warp knit fabrics which are dyed before use. When small molecule dyes are used for these fabrics, uniform dyeing can usually be achieved without great difficulty. However, for some critical dye applications such as fabrics for swimwear and auto upholstery which require excellent wash and/or light fastness, it is desirable to use large molecule acid dyes. In dyeing these fabrics with large molecule acid dyes, even a small amount of non-uniformity in dye uptake of the flat yarns can result in highly-visible non-uniformity in fabric dyeing and thus poor fabric appearance.

Nylon flat yarns generally have break elongations of less than about 60% and thus may be referred to as "fully drawn" yarns. Typically, the high degree of orientation in known flat yarns is imparted by drawing during yarn manufacture in an integrated spin-draw process (speed of withdrawal from the spinneret of between about 1400 and 2000 meters per minute (mpm) and wind-up speeds of between about 2500 and 3500 mpm) or in a split process in which a package of yarn spun at a withdrawal speeds of typically less than 1000 mpm is drawn in a separate process using a single-end draw winder. However, the yarns so produced have often been found to be undesirable for critical dye applications such as εwimwear or auto upholstery due to the great care that must be taken during the preparation of such yarns and during the preparation and dyeing of the resulting fabrics to achieve

acceptable dye uniformity.

Equipment has been sold which is capable of drawing of a warp of nylon yarns in a hot water bath. However, while processes using this equipment can increase dye uniformity, the equipment is recognized to have a number of inherent disadvantages. Processes using the equipment are messy and produce a waste stream of polluted water since the yarn finish is removed into water during drawing. Moreover, for use of the yarn in knitting, a finish must be reapplied after drawing. Another serious drawback of equipment which has been sold for wet drawing is that the speed of the process is typically limited to approximately 300-350 mpm by the limited capacity of the equipment to dry the yarns before wind-up.

SUMMARY OF THE INVENTION In accordance with the invention, flat continuous multifilament nylon apparel yarns especially suitable for critical dyed applications and a proceεε for making such yarnε are provided. The proceεε for making the yarnε includeε: εpinning nylon polymer having a relative viscosity (RV) between about 35 and about 80, the εpinning being performed at a withdrawal εpeed (V, ) sufficient to form εpun yarn with a reεidual draw ratio (RDR) _S of less than about 2.75; stabilizing, interlacing, and applying finish to the spun yarn to form a feed yarn having a residual draw ratio (RDR) _F between about 1.55 and about 2.25, the feed yarn having a dynamic length change (ΔL) and shrinkage rate (ΔL/ΔT) which are both lesε than 0 between 40°C and 135°C; dry drawing and εubsequently dry relaxing the feed yarn to form drawn yarn, the dry drawing being performed at a draw ratio between about 1.05 and about (RDR) _F /1.25 and at a yarn draw temperature (T _D ) between about 20°C and about the temperature T _IIr** of said

polyamide polymer, the dry relaxing of the drawn feed yarns being performed at a yarn relaxation temperature (T _R ) between about 20°C and a temperature about 40°C less than the melting point (T _M ) of the polyamide polymer, the relaxation temperature further being defined by the following equation:

T _R (°C) < [lOOO/d - K ₂ (RDR) _D )] - 273

wherein K_ « 1000/(T _IIfL + 273) + 1.25K ₂ and K ₂ - [1000/(T _{II rL} + 273) - 1000/(T _{II r} .„ + 273)]/0.3. (The temperature T _{II fL} and T _{II f **} are determined by measuring the % change in length verεus temperature at constant tension as will be explained in more detail). The dry drawing and the dry relaxing are performed such that the drawn yarn has a boil-off shrinkage (BOS) between about 3% and about 10% and a residual draw ratio (RDR) _D between about 1.25 and about 1.8.

In a preferred form of the invention, the dry drawing and dry relaxing are performed on a warp of said feed yarns.

For feed yarnε of nylon 66 polymers, a preferred relaxation temperature range for a given residual draw ratio of the drawn yarns (RDR) _D may be obtained by assigning a value of 4.95 to K _x and 1.75 to K2 in the equation above. For nylon 6 polymers, a K- _t of 5.35 and K ₂ of 1.95 are suitable values to obtain a preferred temperature range.

In accordance with one preferred process, the withdrawal speed in spinning is εufficiently high that the residual draw ratio of the spun yarn is less than about 2.5. In another preferred form of the invention, the spinning speed of the yarn as spun imparts a residual draw ratio of less than 2.25, most preferably, less thsn 2.0. Usually, a spun yarn with this residual draw ratio haε a dynamic length change (ΔL) and shrinkage rate (ΔL/ΔT)

which are both less than 0 between 40 ^β C and 135°C. Thus, the spinning at the sufficiently high speed thereby stabilizes the spun yarn without additional stabilization treatments and then the yarn as εpun can be uεed aε the feed yarn.

In accordance with another preferred proceεε in accordance with the invention, the εpinning and the εtabilizing are performed εuch that the feed yarn has a draw tension (DT _33% ) less than about 1.2 g/d, especially less than about 1 g/d.

In the procesε of the invention, dry drawing and dry relaxing of the feed yarnε iε performed, preferably in the form of a warp of yarns treated simultaneouεly. Preferably, the dry drawing and dry relaxing iε done in an inert gaseous atmosphere, e.g., air, of about 50% to about 90% relative humidity (RH), more preferably, about 60% to about 80% RH. In the dry relaxation, a relaxation temperature lesε than about T _{II ;} _, especially less than

^T _II , / is used. Preferred conditions in the relaxation result in a boil-off shrinkage (BOS) of the drawn yarnε of between about 3% and about 8% and a reεidual draw ratio (RDR) _D of the drawn yarnε of between about 1.25 and about 1.55. Preferably, the process produces yarns with a dye transition temperature T _dyβ of lesε than about 65°C.

The proceεε in accordance with the invention iε uεeful for moεt nylon polymerε. Preferred nylon polymetε include nylon 66 polymer and nylon 6 polymer. Eεpecially preferred nylon polymers are nylon 66 containing a minor amount of bifunctional polyamide comonomer units or non-reactive additive capable of hydrogen bonding with the nylon 66 polymer.

In accordance with the invention, a flat multifilament apparel yarn of nylon 66 polyamide polymer is provided. The polymer of the fiber has a melting point (T _H ) between about 245°C and about 265°C, is of relative viscosity (RV) between about 50 and about 80 with about 30

to about 70 equivalent NH2-ends per 10 ⁶ grams of polymer. The multifilament apparel yarn is further characterized by a residual draw ratio (RDR) _D between about 1.25 and about 1.55 with an initial modulus greater than about 15 g/d, a boil-off shrinkage (S) between about 3% and about 10%, a C.I. Acid Blue 122 dye transition temperature (T _DYE ) lesε than about 65°C, a C.I. Acid Blue 40 apparent dye diffusion coefficient (D _A ), measured at 25 ^β C, of at least about 20 x 10- ¹⁰ cm/sec, and apparent pore mobility (APM) greater than about [5-0.37 x 10- ⁴ APV] , wherein the apparent pore volume (APV) is greater than about 4 x 10 ⁴ cubic angstroms. In a preferred form of the invention, the apparent pore mobility is greater than about 2. The process of the invention provides highly uniform nylon yarnε which are useful in a wide variety of warp knit and. woven fabrics which must be uniformly dyeable with large molecule dyes. Yarns in accordance with a preferred form of the invention are especially well suited for this use and have a large molecule dye uniformity rating (LMDR) of at least about 6. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a diagrammatical view of equipment useful for making a feed yarn in a proceεs in accordance with the present invention.

Figure 2 is a diagrammatical view of typical commercial warp-draw equipment useful in a process in accordance with the present invention.

Figure 3 is a typical plot (line A) of draw tension (DT) and the corresponding plot (line B) of the along-end draw tension variation (DTV), at room temperature versus draw ratio (DR), percent elongation (E) and residual draw ratio (RDR) _D . Figure 4 are representative plots of percent change in length (Δ length, %) of a nylon feed yarn versus temperature obtained using the Du pont Thermal Mechanical Analyser at a constant heating rate of 50°C per minute and

varying the initial pre-tenεion from 3 mg/denier to 500 mg/denier; wherein, the yarn extendε under tenεionε greater than about 50 mg/d (Figure 4A - top half) and _c b shrinks under tensions less than about 50 mg/d (Figure 4B

- bottom half) .

Figure 5 is representative plots of the dynamic extension rate, (ΔL/ΔT), verεuε temperature for a nylon feed yarn under pre-tenεions of 50 to 500 mg/d obtained 10 using the Du pont Thermal Mechanical Analyser at a constant heating rate of 50°C per minute; wherein, the maximum dynamic extension rate, (ΔL/Δ )max, iε taken, herein, as the onset of major cryεtallization and occurs at temperature T _IIf* (i.e., between about 110-140°C for 15 most nylon yarns).

Figure 6 iε repreεentative plots of the dynamic extension rate (ΔL/ΔT)max verεuε pre-tenεion εtreεε (σ), as deεcribed in Figure 5; wherein, the εlope, d(ΔL/ΔT)max/d(σ) at 300 mg/d, iε taken as a measure of the

20 senεitivity of the drawn feed yarn during the relaxation εtep to varying εtreεε levelε (i.e., to varying % overfeed) .

Figure 7 iε a typical plot (line A) of the percent change in length (Δ Length, %) of a nylon feed

25 yarn versus temperature obtained using a Du Pont Thermal Mechanical Analyser at a pre-tenεion of 300 mg/d; and the corresponding plot (line B) of the dynamic extension rate defined by the inεtantaneouε change in length per degree

30 centigrade (Δ Length,%)/(Δ Temperature, °C)- of line A.

Figure 8 iε a repreεentative plot of the relative cryεtallization rate, dX/dt, verεuε treatment temperature; wherein, the value of dX/dt increaεes, reaching a maximum value at T _c . 3.5 Figure 9 is a graphical representation of the reciprocal of the relaxation temperature (T _R , °C), as given by the 1000/(T _R + 273), versus the residual dr~w ratio of the drawn yarns (RDR) _D . The regions I (ABDE) and

II (AEHI) enclosed by heavy lines illustrate temperature conditions in the relaxation step (T _R ) as related to the drawing step (RDR) _D of the process useful to produce yarns _c with excellent large molecule dye uniformity ratings b

(LMDR) .

Figure 10 (Line A) is a plot of dynamic shrinkage tension (ST), under constant length conditionε at a heating rate of 30°C per minute versus temperature,

10 which increases sharply at temperature T _g and reaches a maximum at T _sτ,ιn , _x ; and Line B is the corresponding derivative, d(ST)/d(T), of the dynamic shrinkage tension (ST) versus temperature (T) plot (Line A). The derivative plot (B) exhibits minimum values which correspond

15 approximately with temperatures T _{l l r lt} and T _{II f **} , respectively, and a broad maximum which corresponds approximately, with the range between temperatures T _{ι τ *} and τ _c .

Figure 11 is a typical plot of dry heat

20 shrinkage measured uεing the Lawson-Hemphill TYT by increasing temperatures stepwise from 70°C to 150°C.

Figure 12 is a typical plot of the logarithm of the dynamic modulus (E') versuε temperature (line A) and of the corresponding logarithm of the Tan Delta versus

25 temperature (line B).

Figure 13 is a typical plot of the change in heat flow versuε temperature aε measured by Differential Scanning Calorimetry (DSC). An inεet enlargement of

30 temperature range of 60°C to 200°C εhowε three thermal transitions attributed to T _IIfL , T _{II (*} and 1 _{τ τ t} _ _* , respectively.

Figures 14 and 15 are typical plots of the TMA dynamic extension rate versuε temperature for drawn yarns; 35 wherein the drawn yarns of Figure 14 have a LMDR lesε than 6 and those of Figure 15 have a LMDR greater than 6.

Figure 16 is a representative plot of the residual draw ratio of as-spun nylon 66 yarns (RDR) _S

expressed by its reciprocal, 1/(RDR) _S , (line A) and of density (line B) versus spin speed.

Figure 17 is a representative plot of the length change after boil-off of freshly as-spun yarns (line A) and of birefringence (line B) versuε εpin εpeed.

Figure 18 is a repreεentative TMA plot of the dynamic extension rates (ΔL/ΔT) under a 300 mg/d tension versus temperature for various spun-oriented and partial drawn yarns used in the Exampleε aε feed yarnε for warp drawing.

Figure 19 iε a repreεentative TMA plot of εhrinkage (Δ Length,%) versus temperature under a 5 mg/d tension for different yarn types. Figure 20 is a representative plot of draw stress (σ _D ) , expresεed aε a grams per drawn denier (g/dd), versus draw ratio at 20°C, 75°C, 125 ^β C, and 175°C; wherein, the slope is called the draw modulus (M _D ) and is defined by (Δσ _D /ΔDR).

Figure 21 compareε the draw εtresε ( σ _D ) versus draw ratio (DR) at 75°C for various feed yarnε.

Figure 22 iε a repreεentative plot of the logarithm of draw modulus, ln(M _D ), versuε [1000/(T _D , ^β C + 273)] for the feed yarn in Figure 21; wherein, the εlope is taken as a meaεure of the draw energy (E _D ).

Figure 23 (Line A) iε a repreεentative plot of percent dye exhauεtion (%E) for C.I. Acid Blue 122 verεuε dye temperature (°C) with an increaεe in dye exhauεtion occurring at about 57-58°C which correεpondε to the dye bath temperature to reach about 15% exhauεtion referred herein to as the dye transition temperature, T _DXE . Figure 23 (Line B) is a corresponding plot of Line A expreεεed aε percent exhaustion on a logarithimic scale versuε the reciprocal of the dye bath temperature expresεed aε 1000/(T+273).

Figure 24 is a representative plot of dye bath exhaustion curves similar to Figure 23 (Line A), versuε

temperature for four drawn yarns made from Feed Yarn "G" in Table I.

Figure 25 is a representative plot of measured _c dye rate (S ₂₅ ) using a large molecule acid dye C.I. Acid b

Blue 40, versus the residual elongation of drawn yarns made from different feed yarns.

Figure 26 is a plot of the Apparent Pore Mobility (APM) , derived from the orientation of the

10 amorphous polymer chain segments, versus the Apparent Pore Volume (APV) , derived from the wide-angle x-ray diffraction scans, for different drawn yarns listed in Table X.

Figures 27-36 are computer generated simulationε

15 of fabric streaks useful as a guide to determine the LMDR of yarns produced in the examples of this application.

DETAILED DESCRIPTION Nylon polymer as used in this application refers to any of the various generally linear, aliphatic

²⁰ polycarbonamide homopolymerε and copolymerε which are typically melt-spinnable to yield fibers having properties suitable for textile applications. Preferred nylon polymers are poly(hexamethylene adipamide) (nylon 66) and poly( ε-caproamide) (nylon 6). The nylon polymer has a 5 relative viscosity (RV) when spun of between about 35 and about 80.

When nylon 66 polymer is used, it is advantageous for the RV of the polymer to be greater than

30 about 46 as taught in U.S. Reissue Patent No. 33,059 (U.S. Patent No. 4,583,357), the disclosure of which iε hereby incorporated by reference. However, the RV uεually should be less than about 65 since the advantages obtained in accordance with Reissue Patent 33,059 do not increase

35 significantly at above an RV of 65. Also when spinning nylon 66, it is advantageous to use nylon 66 including a minor amount of one or more different copolymer units such as ε-caproamide and/or 2-methyl-pentamethylene adipamide

(Me5-6) or an unreactive additive capable of hydrogen bonding with the nylon 66. For a given εet of εpinning conditions for spinning the feed yarn, this provides an

-. increase in the elongation to break and, for a given b elongation to break, decreases the draw tension which facilitateε drawing in the warp draw εtepε of the proceεε. Due to the ability to obtain the εame feed yarn propertieε with polymer having a lower RV, especially at higher εpin

10 speeds, the use of 2-methyl-pentamethylene diamine to provide 2-methyl-pentamethylene adipamide units in the 66 nylon polymer is especially preferred. Using a Me5-6,66 copolymer feed yarn in the warp draw procesε, the draw tensions decrease at the same draw ratio, an indication

15 that mechanical quality of the drawn yarn should be improved. As the amount of Me5-6 iε increaεed, the dye depth increases. This indicateε that the dye rate increases as the amount of Me5-6 iε increased or that the εtructure iε more open, which iε usually an indication of

20 improved dye uniformity. The shrinkage of the drawn yarn increaseε as the amount of Me5-6 increases, reaching a level of >10% BOS at 20% Me5-6. This level is difficult to obtain with nylon 66 at draw ratios which give good mechanical quality. Alternately, cross-branching agents

25 as disclosed in U.S. Patent No. 4,721,650 can be used if desired. As iε well known in the art, opacifierε εuch aε titanium dioxide, colorants, antioxidantε and other uεeful additives can be incorporated into the polymer.

30 Nylon 66 with a bifunctional copolyamide comonomer capable of hydrogen bonding with the 66 nylon polymer can be prepared by condensation polymerization in an aqueous "salt" solution containing the monomers in appropriate proportions. Procedures useful for the 35 production of homopolymer nylon 66 can be applied to the production of the N6,66 with ε-caprolactam added to the salt solution. To make Me5-6,66, adipic acid with hexamethylene diamine (HMD) and 2-methyl-pentamethylene

diamine (MPMD) in the molar proportions necessary to produce the copolymer with the desired weight percent 2-methyl-pentamethylene adipamide is used to make the salt solution. For Me5-6,66, it is generally necesεary, however, to modify the uεual nylon 66 procedureε to make sure that the MPMD, which iε more volatile, εtayε in solution sufficiently long to react. 2-methyl-pentamethylene diamine is commercially available and is sold by E. I. du Pont de Nemours & CO., Wilmington, Delaware, under the trademark DYTEK X5>.

With reference to Figure 1 which illustrateε the process including alternatives for making feed yarnε, yarn Y is spun from spinneret 1 using a high speed melt spinning process. The filaments are cooled in a "quench" chimney using cross-flow air at, for example, 20°C, and are converged at a finish applicator such aε a roll or metered finish applicator. in accordance with the proceεs of the present invention, the withdrawal speed (V _s ) , i.e., the speed of the first roll which actε to pull the yarn away from the spinneret 1, is sufficient to form spun yarn with a "residual draw ratio" (RDR) _S of less than about 2.75. As will be explained hereinafter, the first roll may be any of a number of different rolls depending on the εpecific equipment uεed. "Residual draw ratio" aε uεed in this patent application refers to the the number of times the length of the yarn may be increased by drawing before the yarn breaks and may be calculated from elongation to break in % (E _B ) by the following formula:

RDR - 1 + (E _B /100)

It has been discovered that the residual draw ratio (RDR) _S must be less than 2.75 in the spun yarn and be combined with the other steps of the process of the method to obtain the improved large molecule dye uniformity in the

drawn yarns. Preferably, the residual draw ratio (RDR) _S is less than about 2.5 in the spun yarn, most preferably less than about 2.25.

The withdrawal speed at which the residual draw ratio of less than 2.75 is imparted to the spun yarn depends on a number of factors in the εpinning proceεε including the fineneεε (denier per filament) of the yarnε being εpun, the relative viεcoεity of the polymer, the spinning temperature, spinneret capillary dimensionε, and the efficiency of the quench aε determined by the quench air flow pattern, flow rate, and quench air temperature. A typical minimum withdrawal εpeed to impart a residual draw ratio (RDR) _S of less than 2.75 iε on the order of about 2000 mpm for normal textile yarns. In general, it iε preferable to spin the feed yarns at withdrawal speeds above about 3000 mpm where it is not aε neceεεary to carefully control proceεε conditionε.

In the proceεε of the invention, the εpun yarn iε stabilized to provide a feed yarn having reεidual draw ratio (RDR) _F of between about 1.55 and about 2.25 and a dynamic length change (ΔL) and εhrinkage rate (ΔL/ΔT) which are both less than 0 between 40°C and 135°C. Preferably, the feed yarn has a residual draw ratio (RDR) _r of between about 1.55 and about 2.0.

As shown in Figure 1 in broken lines, stabilization may be performed by means of a number of different alternativeε. Stabilization can be accompliεhed as indicated in alternative A by exposing the spun yarn to steam in a steam chamber 4 as diεcloεed in U.S. Patent No. 3,994,121 or paεεing the yarn through a εteamleεε, heated tube aε diεclosed in U.S. 4,181,697. The yarn then pasεes through puller and letdown rolls, 5 and 6, respectively, although it is not drawn to any subεtantial extent.

Alternative B indicateε a εet of puller and letdown rollε 5 and 6 which are driven at eεεentially the εame εpeed aε the wind-up and thus there is no εubεtantial drawing of

the yarn between these rolls and the windup. Stabilization is thereby imparted by the high spinning speed as in alternative C, e.g., greater than about 4000 mpm. The rolls 5 and/or 6 could be heated if desired for the purpose of stabilizing the yarn shrinkage if spun at speeds lower than approximately 4000 mpm. Alternative C is a "godetless" process in which the yarn iε not contacted by rolls between the spinneret and the wind-up. The windup εpeed iε sufficient that the spin orientation imparted to the yarn in spinning is sufficient to provide a stable feed yarn without other separate stabilization steps being required. Typical speeds to accomplish this are above about 4000 mpm.. Yarns produced by alternatives B and C are often referred to as spin-oriented or "SOY" yarns. Alternative D illustrates the use of "partial drawing" to stabilize the yarns. Before the letdown rolls 6, feed rolls 7 and draw rolls 8 draw the yarn sufficiently for stabilization. The amount of draw necessary to accomplish this iε between about 1.05 and about 1.8 depending on the orientation in the yarn due to the εpeed and conditions of spinning. Yarns produced by alternative D are often referred to aε "partially-drawn" or "PDY" yarnε. Variations of the stabilization alternatives described are posεible within the method of this invention.

The yarns are interlaced at interlace jet 9 so that the feed yarn haε a εufficient degree of interlace to enable efficient wind-up of feed yarnε at wind-up 10 and removal of the feed yarns from the bobbin for warp-drawing. A suitable level of interlace for this purpose, measured by the rapid pin count (RPC) method, is an RPC interlace of not more than about 14. While interlace can be increased such as by employing a

"tanglereed", in the case of warp-drawing, as desired for further processing or use in fabric formation, a high degree of interlace in the feed yarns iε deεirable when

practical to eliminate the need for such additional interlacing. Thus, the interlace level in certain preferred feed yarnε εhould be high enough to obtain the deεired amount of interlace after the drawing extendε the distance between the interlace nodes. The preciεe amount of interlace for this purpose will generally depend on the yarn filament count and dpf, the type of yarn finish, and the draw ratio and draw tenεion experienced by the yarn, and on propertieε deεirable in the final fabric containing the drawn yarnε, eεpecially for aesthetic purposes. For many feed yarnε, it iε advantageous to employ an RPC interlace of between about 6 and about 10.

In accordance with the preferred form of the invention, the feed yarns are asεembled into a warp after εpinning. For thiε to be accomplished efficiently, it iε advantageous to package the feed yarns on a number of generally uniform length packages which can be supplied from a creel to form a warp of the yarns.

In the procesε of the invention, the feed yarnε undergo dry drawing and dry relaxing to provide drawn yarnε, preferably aε a warp of feed yarnε being treated εimultaneouεly. "Dry" drawing and "dry" relaxing aε uεed in this application iε intended to indicate that the drawing and relaxation is done in a gaseous environment without the application of liquid water to the yarns. The preferred atmoεphere for dry drawing and dry relaxing in accordance with the invention is an inert gaseouε atmoεphere such aε air having a relative humidity between 50 and 90%, preferably between 60 and 80%. The dry drawing and dry relaxing can be done in the preεence of other inert gases such as steam which can provide a εource of heat as well as an inert atmosphere. The yarns are drawn at a draw ratio (DR) of between about 1.05 and about (RDR) _r /1.25. "Draw ratio" (DR) in this application can be calculated from the "total draw ratio" (TDR) which is defined to be the ratio of the

residual draw ratio of the feed yarns (RDR) _r to the residual draw ratio of the drawn yarnε (RDR) _D produced by the process, i.e., after they undergo relaxation:

TDR - (RDR) _F /(RDR) _D

The total draw ratio (TDR) is related to the draw ratio (DR) aε expreεεed in the following equation:

TDR - DR (1-%OF/100)

(%OF refers to overfeed discussed in more detail hereinafter.) The draw ratio (DR) may also be calculated from the length change which the yarn iε subjected to, e.g., the ratio of the speeds of draw rollε to feed rolls, respectively.. Similarly, the total draw ratio (TDR) may be calculated from the speed of the rolls after relaxation to the feed rolls, respectively.

The temperature of the yarn (T _D ) during drawing is between about 20°C and about the temperature T _{II (} __ of the polymer. As illustrated in Figure 7 and accompanying deεcription hereinafter, and in the teεt methodε, T _ZI , _** iε a temperature of the nylon polymer defined by measuring the change in length of the yarn verεus temperature at constant tension. Heating during the dry drawing can be advantageouε to decreaεe the draw tension in the process of the invention. Preferably, the temperature of the yarn during drawing iε most preferably less than about T _IIfL . For nylon 66 and nylon 66 with minor amountε of hydrogen bonding conεtituentε, the temperature of drawing can be up to about 175°C. Preferably, the temperature iε between about 20° and about 135°C, moεt preferably, between about 20°C and about 90°C. For nylon 6, yarn draw temperature εhould generally be about 20-40°C leεs than corresponding temperatures for nylon 66. Non-contact or contact heating apparatus such as ovens, radiant heaters, plate heaters,

hot rolls, microwave heaterε and the like are εuitable for heating the yarn during drawing.

The yarn iε εubjected to a heated relaxation εtep to control boil-off εhrinkage and the relaxation alεo causes the residual draw ratio of the drawn yarns (RDR _D ) to increase slightly. The draw ratio (DR) in the dry drawing and the conditions in the dry relaxing are εelected εuch that the drawn yarnε have a boil-off εhrinkage (BOS) between about 3% and about 10% and a reεidual draw ratio (RDR) _D between about 1.25 and about 1.8. Preferably, the boil-off εhrinkage iε between about 3 and about 8% and the reεidual draw ratio of the drawn yarnε (RDR) _D iε between about 1.25 and about 1.55. In addition, in the drawing and relaxation in accordance with the invention, other yarn propertieε can be adjusted for deεired end uεe. The invention iε capable of providing a range of break elongationε and other deεired propertieε while maintaining uniformity in the yarn which can yield dyed fabricε with good dye uniformity. Preferably, tenacitieε of the drawn yarnε are above about 2 g/d and can be aε high aε about 6 g/d or higher. Preferred moduluε levels are above about 15 g/d and can range up to about 40 g/d or higher.

The % overfeed in the relaxation εtep of the proceεε, i.e., the amount of length change allowed to occur through εhrinking, muεt be εelected to obtain the propertieε deεired. The % overfeed can be εet by adjusting the speed of rollε in contact with the yarn before and after the relaxation and the εhrinkage iε generally decreaεed with increaεing overfeed. Depending on the orientation of the yarn when it reacheε relaxation step and the desired drawn yarn propertieε, the overfeed can be very εmall and rangeε up to about 10%. Preferably, the % overfeed iε between about 2 and about 8%. While the % overfeed can vary within theεe rangeε, the % overfeed εhould not be too high for the particular feed yarn and

relaxation temperature or the tension on the yarns in the relaxation step will drop to zero and the procesε will not run. The appropriate control of overfeed iε also important if a tanglereed is used, εuch aε in warp drawing, to impart additional interlace to the yarnε εince lower relaxation tension giveε tighter entanglement. With the tanglereed the overfeed εhould be adjuεted to give a relaxation zone tension of 0.25 to 0.50 grams/drawn denier (g/dd) or preferably 0.30 to 0.375 g/dd. At relaxation zone tension below ~0.25 g/dd, operability with the tanglereed is poor.

In the procesε of the invention, the temperature of the yarnε during relaxation (T _R ) muεt be between about 20°C and a temperature about 40°C less than the melting point of the nylon polymer (T _H ). As in the drawing εtep of the procesε, non-contact or contact heating apparatus such as ovens, radiant heaters, plate heaters, hot rollε, microwave heaters, and the like are suitable for heating the yarn during relaxation.

It haε been discovered that controlling the yarn temperature during relaxation (T _R ) to correspond in a particular relationship to the residual draw ratio of the drawn yarns (RDR _D ) provides high large dye molecule dye uniformity ratingε. In accordance with the invention, the relaxation temperature (T _R ) iε εelected in accordance with following relationεhip:

T _R (°C) < [lOOO/tKj - K ₂ (RDR) _D )J - 273

wherein K _x - 1000/(T _{II rL} + 273) + 1.25K ₂ and K ₂ = [1000/(T _{II rL} + 273) - 1000/(T _IIf .„ + 273)1/0 _* 3, preferably, the yarn relaxation temperature iε less than ^τ n, _** ^an< * ^is roos preferably less than T _{II (} _. T _H , T _{II fL} , Tn _{. **} and T _{II( *} are determined on feeds yarns of the nylon polymer being employed as illustrated in Figure 7 and accompanying text and in the Test Methods which

follow.

For feed yarns of nylon 66 polymers, a preferred relaxation temperature range for a given residual draw ratio of the drawn yarns (RDR) _D may be obtained by assigning a value of 4.95 to K _x and 1.75 to K2 in the equation above. Preferred relaxation temperatures are less than about 175°C and, most preferably, leεε than about 135°C for nylon 66 or nylon 66 with a minor amount of a hydrogen bonding constituent. For nylon 6, a preferred temperature range may be defined by asεigning the values of 5.35 to K _x and 1.95 to K ₂ , respectively. In general, the preferred temperatures for nylon 6 yarns are 20-40°C leεε than correεponding temperatureε for 66 nylon. Commercially available equipment haε been found to be εuitable for warp-drawing of appropriate feed yarnε in accordance with the invention. A model DSST 50 manufactured by Karl Mayer Textilmaεchinenfabrik GmbH, D-6053 Obertεhauεen, Germany, and a model STFl manufactured by Barmag Aktiengeεellshaft, 5630 Remscheid, Germany, are εuitable and the uεe of both iε illustrated in the examples which follow. Typical wind-up speeds for such equipment are in the range of up to about 600 mpm. Since the equipment is εimilar, only the Barmag STFl iε εhown εchematically in Figure 2.

With reference to Figure 2, a warp sheet of feed yarn (indicated by the character W) is pulled by feed rolls 11-13 from a creel (not shown) on the left. Feed roll 13 is heatable and is uεually heated to a temperature of between about 50 and about 90 ^β C. An inclined plate heater is provided in this unit and can be uεed to further heat the yarnε if desired. The warp of yarn W is then advanced to unheated draw rolls 14-17. The draw rolls 14 and 15-17 are driven at a greater speed than the feed rolls to impart the deεired amount of draw to the warp of yarnε.

After passing draw roll 17, the yarnε undergo

relaxation as they pass in a warp in contact with a plate heater which has the capability, for this particular warp draw model, to be heated up to about 200°C. The amount of relaxation is controlled by exit rolls 18-20 which are driven at a εpeed appropriately leεε than that of the draw rolls 14-17 to provide the desired overfeed. The resulting yarnε are wound up simultaneously as a beam at a beam winder (not shown). For the equipment illustrated in Figure 2, the warp sheet of feed yarnε is drawn between rolls 13 and 14 at a draw temperature (T„) with a warp draw ratio (WDR) defined by the ratio of the surface speedε of rollε 13 and 14 (i.e., WDR - V14/V13; heat relaxed between rollε 17 and 18 at a relaxation temperature (T _R ) and with a percent overfeed, %OF - (1-V18/V17)100, where V18/V17 iε the ratio of the εurface εpeedε of rolls 17 and 18; and providing a total warp draw ratio TWDR given by the expresεion: TWDR - WDR x (1-%OF/100) - <V14/V13)X(V18/V17) - V18/V13, εince typically Vl4 - V17.

Yarns produced in accordance with the invention have properties which make them extremely well-suited for critical dye application. A number of physical properties of the yarns are responεible for the uniform dyability and any one or more of which are very important to the uniformity in dying. Two propertieε which are believed to be characterisric of the process and the yarns produced by the procesε of the invention are an along-end %CV of leεε than about 0.7 by denier variation analyεiε (DVA) for both the feed and drawn yarnε and an along-end %CV of draw tension of less than about 1.0 when drawn 1.33X (DT _33% ) for the feed yarn.

The preferred method in accordance with the invention provides yarns which have a "large molecule dye uniformity rating" (LMDR) of at least about 6. The term "large molecule dye" refers to either Anthraquinone Milling Blue BL (C.I. Acid Blue 122) or Sandolin Milling

Blue BL-N (CI. Acid Blue 80). Both of these dyes are large molecule, waεh-faεt, rate-εensitive acid dyes. Although not useful for measurement of LMDR in this _c application, other large molecule acid dyeε may be more or leεs critical. "Large molecule dye uniformity rating" (LMDR) as uεed in the present application refers to a yarn dye uniformity evaluation made by knitting the yarnε into a tricot fabric and dyeing uεing either of the above large

10 molecule dyes. After dyeing in the evaluation procedure, the fabric is rated by a panel of expertε on a scale from 1 to 10 as deεcribed in more detail in the test methods which follow using computerized si ulationε of fabric streaks shown in Figures 27-36 as a guide. A rating of 5

15 or below is considered unacceptable and a rating of 5 to 6 is considered borderline acceptable for some non-critical warp knit fabrics. A rating of 6 or more is considered acceptable for most warp knit fabricε. A rating of 6.5 or more iε considered acceptable for critical warp knit

20 fabrics such as thoεe used for εwimwear and it iε more preferred for yarnε in accordance with the present invention to reεult in a uniformity rating of above about 6.5. A rating of 7 or greater iε considered superior and yarns in accordance with the invention which can yield a

25 rating of over 7 are most preferred. Ratings as high as 8.0 and greater are posεible in accordance with the preεent invention.

Figure 3 iε a typical plot of draw tenεion, DT

30 (line A), meaεured at room temperature (expreεεed aε gramε per original denier), for a nylon feed yarn having an elongation-to-break (E _b ) of 80% (i.e., a (RDR) _F - 1 + 80/100 - 1.80) plotted verεuε percent elongation (E), draw ratio (DR = 1 + E/100), and residual draw ratio of the 35 drawn yarn [(RDR) _D = (RDR) _f /DR_; wherein, DT initially increases sharply with draw ratio up to yield point (Ey,i) at about 5% E (i.e., at about 1.05x DR), and increaεeε less with draw ratio upto break at Eb (i.e., RDR ■ 1.0);

and of the corresponding plot (line B) of the along-end draw tension variation (DTV), expresεed as % CV, which decreases sharply to the initial yield point (Ey,i) and remains essentially constant over the yield region Ey,i to Ey,f and then typically increaseε until the yarn breakε. The optimum draw zone iε defined by Ey,i to Ey,f; that iε, in thiε example by E-valueε of 5% to 55%, equivalent to a (WDR)min of 1.05 to a (WDR)max of 1.44 (- 1.8/1.25), correεponding to a (RDR)max of 1.71 (« 1.8/1.05) to a (RDR)min of 1.25, respectively.

Figures 4A and 4B are representative plots of percent change in length (Δ length, %) of a nylon feed yarn versus temperature obtained using a Dupont Thermal Mechanical Analyzer (TMA) at a constant heating rate of 50 ^β C per minute (+ 0.1 ^β C) and varying the pre-tenεion (alεo referred herein aε stresε, σ, expressed aε mili- grams per original denier) from 3 mg/denier to 500 mg/denier; wherein, the yarn extends under pre-tenεionε greater than about 50 mg/d (Figure 4A - top half) and εhrinkε under pre-tensions less than about 50 mg/d (Figure 4B - bottom half).

The instantaneous length change response versuε temperature for a give tension, [(Δ Length, %)/(Δ Temperature, °C)J ■ [Δ L/Δ T], iε herein referred to aε the "dynamic εhrinkage rate" under shrinkage condtionε and aε "dynamic extenεion rate" under extension conditionε. The preferred feed yarnε used in thiε invention εhrink under an initial tenεion of 5 mg/d between 40°C and 135°C, corresponding approximately to the glasε transition temperature (Tg) and the onset of major crystallization (T _{1I f} .); and have a dynamic shrinkage rate less than zero under the same conditionε (that iε, εhrinkage increaεes with temperature and does not exhibit any εpontaneous extension after initial shrinkage between about 40°C and 135°C) .

Figure 5 is a representative plot of the TMA

dynamic extenεion rate, (ΔL/ΔT), verεuε temperature for a nylon feed yarn under tenεionε of 50 to 500 mg/d (refer to Figure 4 for detailε). The maximum dynamic extenεion rate, (ΔL/ΔT)max, is taken, herein, aε the onset of major cryεtallization and occurε at temperature T _{II# *} . The preferred draw temperature (T _D ) iε lesε than about T _{IIf *} .

Figure 6 is a repreεentative plot of the maximum TMA dynamic extension rates, (ΔL/ΔT)-,, _x , versus initial stress, expresεed aε iligramε per original denier; wherein, the (ΔL/ΔT) _Bax increases with increasing streεε (σ) aε characterized by a positive slope, d(ΔL/ΔT),, _x /dσ. The value of d(ΔL/ΔT) _Bax /dσ decreaseε (Line E to Line A) in general with increaεing polymer RV, and increaεing εpin εpeed (i.e., decreaεing (RDR) _S . Preferred feed yarnε uεed in thiε invention are characterized by (ΔL/ΔT) _Bax valueε leεs than about 0.20, preferably between about 0.15 and about 0.05 %/ ^β C, and d(ΔL/ΔT) _» , _x /dσ values, between about 3 x 10-« and about 7 x 10-* (%/ ^β C)/(mg/d) at a stress (σ) of 300 mg/d which is selected to characterize the preferred feed yarns of the invention since it is typically the nominal tension level in the relaxation zone (between rolls 17 and 18 in Figure 2).

Figure 7 (Line A) is a typical plot of the percent change in length (Δ Length, %) of a nylon feed yarn versus temperature (°C) obtained using a Du Pont Thermal Mechanical Analyser at a constant heating rate of 50°C per minute (+/-0.1 ^β C) under constant tension of 300 miligrams per original denier. The onset of extension (i.e., ΔL > 0) occurs at about the glass transition temperature (Tg) and increaseε sharply at a temperature Tn _rL which is believed to be related to the temperature at which the hydrogen bondε begin to break permitting extenεion of the polymer chainε and movement of the crystal lamellae.

Figure 7 (Line B) iε a plot of the correεponding TMA dynamic extenεion rate to line A, herein defined by

the instantaneous change in length per degree centigrade,

(Δ length,%)/(Δ temperature, ^β C) ■ (ΔL/ΔT), the dynamic extension rate, (ΔL/ΔT), iε relatively conεtant between Tg and the T _{x h} , and then riεeε to an initial maximum value ' at a temperature T _{II f} «, which iε believed to be aεεociated with the onεet of major cryεtallization. The dynamic extension rate remains esεentially constant at the higher level over the temperature range T _{Σ τ t *} to T _{II fϋ} and then riseε εharply at T _IIfU which iε aεεociated with the onεet of cryεtal melting and softening of the yarn, until the yarn breaks under tension at a temperature typically less than the melting point (T.); wherein, T _{II fU} is 40 ^β C leεε than T _Λ . Moεt aliphatic polyamides exhibit the dynamic extension rate versuε temperature behavior of line B, wherein, there is a slight reduction in the dynamic extension rate, after the initial maximum at T _XI ._ reaching a minimum at temperature T _IZ(* », which for nylon 66 polyamides is frequently referred to as the Brill temperature and is associated with the transformation of the lesε thermally stable Beta-crystalline conformation to the thermally more stable Alpha-crystalline conformation; and for nylon 6 polyamides, temperature T _{II( **} iε believed to be associated with the transformation of the Gamma-crystalline conformation formed only via spin-orientation to the more stable Alpha-crystalline formation typical of drawn and/or thermally treated yarns.

The preferred draw conditionε for critical acid dyeability have been found to relate to the careful balancing of the extent of drawing (aε given by DR) , the draw temperature (T _D ), the relaxation temperature (T _R ), and the extent of relaxation permitted (as given by % overfeed, %OF, or by the extent of relaxation, 1-%OF/100). Herein, the preferred ranges are: DR between about 1.05X and (RDR) _F /1.25; T _D of 20°C to lesε than about l„ ..,

preferably less than about T _{II (} . and especially lesε than about T _IIrIt ; T _R lesε than about T _1I#U (i.e., T _M -40°C), preferably leεε than about T _{II f **} , and eεpecially lesε than about T _{x z t *} .

The requirement to reduce T _R with decreasing (RDR) _D (i.e., increasing DR and decreasing %OF) is believed to be associated with the shifting of the distribution of pore sizeε between cryεtalliteε to εmaller valueε which decreaεeε the rate of dye diffuεion (herein expreεεed by the yarn MBB value) and increaseε the temperature of the onset of major mobility of the pores (herein related to the dye transition temperature, T _DYC , and to the temperature at the maximum dynamic modulus (T _E"» . _X ). it iε believed that there exists a combination of distribution of pore-sizes and mobility of the pores that defines critical acid dyeability. Thiε combination iε believed to be achieved by the proper selection of feed yarn and by the draw process of the invention.

Figure 8 iε a representative plot of the relative cryεtallization rate, dX/dt, versus treatment temperature. The value of dX/dt increases, reaching a maximum value at T _c which is approximately 150*C for nylon 66 and 146 ^β C for nylon 6. Temperatures T _x and T ₂ denote treatment temperatures where the relative extent of cryεtallization X - 1/2. For nylon 66 T ₂ and T _j are about T _c +/- 40 ^β C, and for nylon 6 T ₂ and T _x are about τ _c +/- 20°C. Between the temperature !!__ , and T _c , cryεtallization proceeds via nucleation and continues via growth of the existing crystals between τ _c and T ₂ .. Comparing Figures 8 and 7, suggeεtε that T _IItL and T _{II rU} may correεpond to T-*. , and T ₂ . , reεpectively; and that ^τ n,*, a ¹¹ "* ^{1 τ} n,** ^a Y correεpond to T _x « and T ₂ *. , reεpectively. Although thiε invention iε not tied to any particular theory, it iε believed that the preferred relaxation temperature in draw iε leεε than about T _c , i.e., under conditionε of uniform nucleation versus

cryεtal growth, eεpecially aε the (RDR) _D of the drawn yarn iε reduced.

Figure 9 iε a graphical representation of the _ς reciprocal of the relaxation temperature (T _R , °C), aε given by the 1000/(T _R + 273), verεuε the residual draw ratio of the drawn yarns (RDR) _D . The regions I (ABDE) and II (AEHI) encloεed by heavy lineε illustrate temperature conditionε in the relaxation εtep (T _R ) aε related to the

10 drawing εtep (RDR _D ) of the process useful to produce yarnε with excellent large molecule dye uniformity ratingε (LMDR). Line BCD corresponds to room temperature (RT), line AME corresponds to T _{II |} (about 90°C), line KLF correspondε to T _{II ( *} (about 135°C), line JG correεpondε to

15 τ _{II ( **} (about 175°C) and line IH corresponds to T _{II fϋ}

(about 225°C for nylon 66 polyamides or about TM-40°C for other polyamides. Line AKJI corresponds to the equation: [1000/(T _R + 273)] K _x - K ₂ (RDR) _D which may be re-arranged to give the expression: T _F (°C) [lOOO/fK _j -

20 K ₂ (RDR) _D )] - 273 wherein, K _x - 1000/(T _IIfL + 273) + 1.25K ₂ and, K ₂ - tl000/(Ti _lfll + 273) - 1000/(T _IIt** + 273)]/0.3. For most nylons the values of K _x and K ₂ are about 4.95 and 1.75, reεpectively. For nylons with lower melting points (T _H ), such as nylon 6 with a melting point

25 about 40°C lower than that of nylon 66 homopolymer, the values of T _IIfL and Tj*-*. _* . are typically lower giving different values for K and K ₂ (see Figure 18 for comparison of TMA curves for high speed spun nylon 6 and .

20 nylon 66 homopolymerε) .

Figures 10 thru 13 are representative thermal responεeε of nylon feed yarnε showing similar thermal transitionε aε in Figure 6. Figure 10 (Line A) iε a plot of dynamic εhrinkage tenεion (ST), under conεtant length

35 conditionε at a heating rate of 30 ^β C per minute verεuε temperature, which increaεes sharply at temperature Tg and reacheε at maximum value at T _STlB , _x and then decreaεes εharply to a temperature, here denoted as T _IIfL and

continues to decreaεe leεs sharply between T _1I(Il and a temperature, here denoted as T _{II (} « _* and then decreaseε more rapidly thereafter. The T _STBajc iε frequently aεεociated with the onεet of major polymer chain mobility and subsequent nucleation. The eεpecially preferred draw temperature (T _D ) iε typically between Tg and T _{1I rL} . Moεt yarns in the examples were drawn near T _STaax . Figure 10 (Line B) is the corresponding derivative, d(ST)/d(T), of the dynamic shrinkage tenεion (ST) versuε temperature (T) plot (Line A). The derivative plot (B) exhibitε minimum values which correspond approximately with T _1IfL and Tn _{, *} ., respectively, and a broad maximum which corresponds approximately with the temperature range of T _π . to T _c .

Figure 11 iε a typical plot of shrinkage measured using the Lawεon-Hemphill TYT by increaεing temperatures stepwise from 70°C to 150 ^β C. The shrinkage increaεeε sharply at about 90°C which is similar to that observed using the Du Pont TMA (see Figure 4). The temperature of the sharp increase in shrinkage is associated with temperature T _IIf .

Figure 12 is a typical plot of the logarithm of the dynamic modulus (E ^r ), Line A, and of the corresponding logarithm of the Loss Tan Delta, Line B, versuε temperature; wherein, both are measured using a rheovibron at a heating rate of 5°C/minute. The characteristic thermal transitions are marked and compared to those obεerved in Figureε 6 and 10.

Figure 13 iε a typical plot of the change in heat flow verεuε temperature as measured by Differential Scanning Calorimetry (DSC). An inset enlargement of temperature range of 60°C to 200°C shows three thermal transitionε attributed to T _{1I rL} , T _1Ir* , and T _{II r *} , _f reεpectively. The onεet of the melting endotherm at about 225°C for thiε nylon 66 yarn iε aεεociated with T _{Il rU} and iε about 40°C lesε than the melting point T _H .

Figureε 14 and 15 are typical plotε of the TMA dynamic extenεion rateε at 300 mg/d pre-tenεion verεuε temperature for the warp drawn yarnε of Exampleε IV-3 and IV-10, respectively; wherein the yarnε of Ex. IV-10 have a LMDR > 6 and the yarns of Ex. IV-3 have a LMDR of lesε than 6 which corresponds to the greater variability of (ΔL/ΔT) versuε temperature between temperatureε A and D, especially between A and C (compare Figure 14 verεuε Figure 15) .

Figureε 16 and 17 are plotε of important aε-εpun nylon 66 yarn propertieε versuε spin speed (V,), but the general behavior iε also found for nylon 6. Figure 16 (line A) is a repreεentative plot of the reεidual draw ratio of aε-εpun nylon 66 yarnε (RDR) _S expreεεed by its reciprocal, 1/(RDR) _S (which is approximately proportional to the degree of molecular chain extension and frequently referred to aε the yarn spun draw ratio) versus spin speed (V, ), and is observed to increase linearly with increasing spin speed (V. ) over the range of 1000 mpm to about 4000 mpm, and then increaseε linearly at a reduced rate versus spin speed over the range of about 4000 to about 8000 mpm. The absolute value of (RDR) _S is known to vary with polymer RV and dpf, for example, but the importance of Figure 16 Line A iε the tranεition in behavior of (RDR) ₈ at about 4000 mpm. Above about 4000 mpm no thermal/mechanical εtabilization iε usually required to provide a stable yarn package. Below about 4000 mpm, the as-spun yarn must be further εtabilized to provide a uεeful yarn package for warp drawing (see diεcuεsion of Figure 1).

In Figure 16 (Line B) the density (p) increaseε with increaεing εpin speed and increaseε more sharply above about 4000 mpm. It is found that feed yarns having a (RDR) _S of the spun yarn lesε than about 2.75, correεponding to 1/(RDR) _S value of greater than about 0.364 are preferred for drawing. Figure 16 does not

alone indicate a reaεon for the requirement of an (RDR) _S value leεε than about 2.75.

Figure 17 (line A) is a repreεentative plot of the length change after boil-off of spun yarns not permitted to age more than 24 hours verεuε spin speed. Up to about 2000 mpm the spun yarnε elongate in boiling water (region I). Between about 2000 and about 4000 mpm the εpun-yarnε elongate in boiling water, but with a leεε extent verεuε εpin εpeed (region II). Above about 4000 mpm, the aε-εpun yarnε εhrink in boiling water (region III) .

In Figure 17 (line B) the correεponding birefringence (Δn) valueε for these yarns are plotted versuε εpin εpeed. There iε observed a reduction in the rate of increaεe in birefringence versuε spin speed at about 2000 mpm which is believed to be associated with the transition between region I and region II behavior and attributed to the onset of stress-induced nucleation on the spin-line. The transition between regions I and II corresponds approximately to an as-spun yarn (RDR) _S of less than about 2.75. Feed yarns with as-spun yarn propertieε indicative of region I can not be "dry" drawn to give LMDR of greater than 6. Yarns used in this invention are of regions II and III and preferably of region III for it is observed that yarns of region III have very little sensitivity to moisture-on-yarn during finish application on dye level (MBB) and their yarn properties are more εtable with time on εtorage.

Figure 18 iε a representative TMA plot of the dynamic extenεion rateε (ΔL/ΔT) under a 300 mg/d tenεion verεuε temperature for variouε feed yarn types: A = nominal 50 RV nylon 66 yarn εpun at 5300 mpm and containing 5% Me5-6; B « nylon 66 homopolymer yarn εpun at 5300 mpm (Yarn J of Example I); C « nylon copolymer yarn spun at 5300 mpm (Yarn K of Example I); D - nylon partial drawn yarn (indicative of Yarnε D-F of Example I); E «

nominal 47 RV nylon 6 homopolymer yarn spun at 5300 mpm. Nylon 6 feed yarnε are εhifted about 20-30 ^β C to lower temperatureε verεuε nylon 66 feed yarns which reduces the maximum relaxation temperature (T _R ) _KAX for nylon 6 by about 20-30 ^β C versuε that for nylon 66 homopolymer.

Figure 19 iε a repreεentative TMA plot of εhrinkage (Δ Length,%) versuε temperature under a 5 mg/ tension for different yarn types. Most feed yarnε εhrink with increaεing temperature eεpecially between 40°C and 135 ^β C; however, Yarn A initially elongates and only shrinks at temperatures above about 150°C. Yarn A is not a preferred feed yarn since it does not shrink, but elongateε between 40 and 135°C (i.e., ΔL > 0); and also since it iε characterized by a positive rate of length change, herein referred to as a "positive dynamic shrinkage rate" (i.e., ΔL/ΔT > 0), °C). Preferred feed yarnε for draw have a negative dynamic length change and a negative dynamic shrinkage rate over the temperature range of 40°C and 135 ^β C.

Figure 20 is a representative plot of draw stress (σ„ ) , expressed as a grams per drawn denier, versus draw ratio at 20 ^β C, 75 ^β C, 125 ^β C, and 175 ^β C. The draw stress ( σ _D ) increases linearly with draw ratio above the yield point and the slope is called herein aε the draw modulus (M _D ) and iε defined by (Δσ _D /ΔDR). The values of draw stress (σ _D ) and draw modulus (M _D ) decrease with increasing draw temperature (T _D ).

Figure 21 compares the draw stress (σ _D ) versus draw ratio (DR) at 75°C for various feed yarnε (A - nominal 65 RV nylon 66 homopolymer spun at 5300 mpm; B - nominal 68 RV nylon 6,66 copolymer spun at 5300 mpm; C - nominal 40 RV nylon 66 homopolymer spun at about 3300 mpm). The desired level of draw εtresε (σ _D ) and draw modulus (M _D ) can be controlled by selection of feed yarn type and draw temperature (T _D ). Preferred draw feed yarnε have a draw εtress ( σ _D ) between about 1.0 and about

2.0 g/dd, and a draw modulus (M _D ) between about 3 and about 7 g/dd, as measured at 75°C and at a 1.35 draw ratio (DR) taken from a plot of draw εtreεε (σ _D ) verεuε draw ratio.

Figure 22 is a representative plot of the logarithm of draw modulus, ln(M _D ), versuε [1000/(T _D , C + 273)] for the three yarnε in Figure 21. The εlope of the linear relations in Figure 22, is taken aε an apparent draw energy (E _D ) _A asεuming an Arrheniuε type dependence of M _D on temperature (i.e., M _D - Aexp(E _D /RT), where T iε temperature in degrees Kelvin, R iε the univerεal gaε conεtant, and "A" iε a material conεtant). Preferred draw feed yarnε have an apparent draw energy (E _D ) _A [- E _D /R =• Δ(lnM _D )/Δ (1000/T _D ), where T _D iε in degrees Kelvin] between about 0.2 and 0.6 (g/dd)/ ^β K.

Figure 23 (Line A) iε a repreεentative plot of percent dye exhauεtion (%E), for C.I. Acid Blue 122, verεuε dye temperature ( ^β C) with an increase in dye exhaustion occurring at about 57-58°C which corresponds to the dye bath temperature to reach about 15% exhaustion herein defined herein aε the dye transition temperature, T _DXE . Figure 23 (Line B) is a corresponding plot of Line A expreεεed aε percent exhauεtion on a logarithmic scale versuε the reciprocal of the dye bath temperature expreεεed aε 1000/(T+273) . The dyeing tranεition temperature iε not aε apparent in the Log (%E) verεuε 1000/(T+273) plot; but the εmoothed near-linear relationεhip permits a more accurate interpolation of the dye transition temperature (T _DYE ), herein defined aε the temperature T (°C) at 15% dyebath exhauεtion (uεing C.I. Acid Blue 122). Figure 24 iε a repreεentative plot of dye bath exhaustion curves (C.I. Acid Blue 122) versus temperature for four warp drawn yarns made from Feed Yarn "G" in Table I; Curve A = 1.15X DR/T _R at 57°C; and Curve B = 1.15X DR/T _R at 177°C; Curve C *= 1.45X DR/T _R at 57°C; and Curve D = 1.45X DR/T _R at 177°C. Yarnε A, B, and C have

T _DYE values less than about 65°C and provide yarns for uniform dyed fabrics, while Yarn D haε a T _DYE value greater than 65°C and doeε not provide dyed fabricε with acceptable uniformity when dyed with large molecule acid dyes.

Figure 25 is a representative plot of measured dye rate (S ₂₅ ) at 25°C uεing a large molecule acid dye, C.I. Acid Blue 40, verεuε the reεidual elongation of warp drawn yarnε made from different feed yarnε; where Line A iε from a feed yarn εpun greater than about 4000 mpm (region III in Figε. 16 and 17; Line B iε from a feed yarn εpun between about 2500 and 4000 mpm (region II in Figε. 16 and 17), and Line C iε from a feed yarn spun lesε than 2000 mpm (region I in Figs. 16 and 17). The dye rate at a given reεidual elongation is observed to increase with the spin speed of the feed yarn uεed in the dry draw/dry relax warp draw proceεε. Drawn yarnε from feed yarn C are nonuniform at all drawing and relaxation process conditions and their nonuniformity is believed to be related to the apparently inherent lower dye rates of the drawn yarns from Region I feed yarns versus that of drawn yarns from feed yarnε of Regionε II and III, and the drawn yarnε having εuch lower dye rates are also found to have T _DYE values greater than 65 ^β C.

Figure 26 iε a plot of the Apparent Pore Mobility (APM) , derived from the orientation of the amorphouε polymer chain εegmentε, versus the Apparent Pore Volume (APV), derived from the wide-angle x-ray diffraction scans, for different drawn yarnε listed in Table X. Drawn yarns providing a LMDR of at least about 6 are found to have a combination of an APM greater than about 2 (Line CC'E) and greater than about (4.75-0.37 x 10- ⁴ APV), Line ABCD; and an APV greater than 4 x 10~ ⁴ cubic angstroms (Line BB'G). Preferred yarns have an APM greater than 2 and greater than (5-0.37 x 10- ⁴ APV), τ.ine A'B'C'D; and an APV greater than 4 x 10~ ⁴ cubic angstroms.

Yarns having combinations of APM and APV, correεponding to region BGFEC, are alεo characterized by a dye transition temperature T _DYE lesε than about 65°C. The following exampleε further illuεtrate the invention and are not intended to be limiting. Yarn properties and proceεε parameterε are meaεured in accordance with the following teεt methodε. Partε and percentageε are by weight unless otherwise indicated. TEST METHODS

The Relative Viscosity (RV) of the polyamide iε measured as described at col. 2, 1. 42-51, in Jennings U.S. Patent No. 4,702,875.

Denier of the yarn is measured according to ASTM Deεignation D-1907-80. Denier may be meaεured by meanε of automatic cut-and-weigh apparatuε εuch aε that deεcribed by Goodrich et al in U.S. Patent No. 4,084,434.

Tenεile Propertieε (Tenacity, Modulus and Break Elongation) are meaεured aε deεcribed by Li in U.S. Patent No. 4,521,484 at col. 2, 1. 61 to col. 3, 1. 6. The Modulυε (M), often referred to aε "Initial Modulus ," is obtained from the slope of the first reasonably straight portion of a load-elongation curve, plotting tension on the y-axiε against elongation on the x-axis. the Secant Modulus at 5% Extenεion (M5) iε defined by the ratio of the (Tenacity / .05) X 100, wherein Tenacity iε meaεured at 5% extension.

Yarn Temperature is measured by a noncontact method using an infrared microscope using the procedure described by Zieminski and Spruiell, J. Appl. Polymer Science, 35, 2223,2245(1988) and Bheda and Spruiell, J. Appl. Polymer Science 39,447-463(1990). Temperature of equipment deεcribed herein, e.g., rollε, etc. iε meaεured with εtandard thermocouples.

Boil-off εhrinkage (BOS). The following relaxed skein method iε used for the feed yarnε described in this application and measures the change in length as a

percentage of the original length of a skein of yarn upon immersion in boiling water. Skeins of yarn are prepared on a standard denier reel of 1-1/8 meters in circumference. The number of revolutions of the reel is determined from the weight used to measure the skein length. The weight εhould be as follows:

<30 denier — 100 g; 30-100 denier — 250 g;

>100 denier — 500 g.

The number of revolutions is that required to give a load of 55 mg/denier and iε calculated from the following formula:

R - 1000W/2LD

wherein R - number of revolutionε rounded to the nearest integer;

W - weight in grams;

D - denier;

L « load ■ 55 mg/denier.

The skeins are straightened by hanging on a hook and attaching the weight. The length of the skein is meaεured to the neareεt 1 mm and recorded aε LI. The εkeins are then wrapped in a cheesecloth and placed in a boil-off pot for 20 + 1 min. at 98 + 1°C. The skeins are removed from the bath and allowed to air dry. The skein length after boil-off, L2, is measured by the same method as Ll. Boil-off shrinkage is calculated aε:

%BOS = (Ll - L2) x 100/Ll

Boil-Off Shrinkage (BOS) The following loop method is used for the measurement of boil-off shrinkage

of the warp drawn yarns. The yarn is tied in a loop having a length of about 50 cm and the length of the loop is measured under a load of 0.05 g/d using a meter stick. The load is removed and the loop iε placed in boiling water with a load of about 0.6 g to prevent it floating and becoming entangled in the water. The loop iε dried in air and the length iε remeaεured under a load of 0.05 g/d. Boil-off εhrinkage iε calculated aε followε:

Length before boiling - Length after boiling

BOS •= X 100

Length before boiling

Heat Set Shrinkage After Boil Off (HSS/ABO) iε meaεured by immerεing a εkein of the teεt yarn into boiling water and then placing it in a hot oven and measuring εhrinkage. More εpecifically, a 500 gram weight is suεpended from a 3000 denier εkein of the teεt yarn (6000 denier loop) εo that the force on the yarn iε 83 mg./denier, and the εkein length is measured (Ll). The 500 gm. weight is then replaced with a 30 gm. weight and the weighted skein is immersed into boiling water for 20 minutes removed and allowed to air dry for 20 minutes. The skein is then hung in an oven at 175 degrees C for 4 minutes, removed, the 30 gm. weight iε replaced with a 500 gm. weight and εkein length iε meaεured (L2). "Heat set shrinkage after Boil Off" is calculated by the formula:

Heat Set Shrinkage After Boil Off (%) « Ll - L2 X 100

Ll Heat set εhrinkage after boil-off (HSS/ABO) iε typically greater than BOS, that iε, the yarnε continue to shrink on DHS at 175°C ABO which iε preferred to achieve uniform dyeing and finiεhing.

Static Dry Heat Shrinkage (DHS90 and DHS135) are measured by the method deεcribed in U.S. Patent No.

4,134,882, Col. 11, 11. 42-45 except that the oven temperatures are 90 degrees C, 135 degrees C, and 175 degrees C, reεpectively, inεtead of 160 degrees C. _c Large Molecule Acid Dye Uniformity (LMDR) Yarnε were knitted into tricot fabric uεing a 32 gauge tricot machine and dyed by the following procedure uεing either C.I. Acid Blue 122 or C.I. Acid Blue 80:

Thiε procedure iε uεed to dye small quantities

10 (~1 - 3 yards) of fabric. A weighed quantity of fabric iε added to 30 literε of water at 110°F in a Cook waεher. To this bath iε added 3 g of Merpol HCS (a liquid nonionic detergent εold by E. I. du Pont de Nemourε and Company) and 3 g of 10% ammoniun hydroxide. The bath temperature

I ⁵ is raiεed to 160°F at 3°F/minute and the cook waεher iε run for 15 minuteε. Then the bath iε emptied and cleared thoroughly and a 30 literε of water iε added. The temperature iε εet at 80°F and 0.5% on weight of fabric of Merpol DA (a non-ionic εurfactant sold by E. I. du Pont de

20 Nemourε and Company) iε added. The bath iε run for 5 minutes to allow mixing, and 2% on weight of fabric of MSP (monobasic sodium phosphate) is added. The pH of the bath iε adjuεted to 6.0 with acetic acid. Then 6% on weight of fabric of ammonium εulfate iε added and the bath iε run

25 for 5 minuteε before adding 1.0% on weight of fabric of Du Pont Anthraquinone Milling Blue BL (CI. Acid Blue 122) or Sandolin milling blue N-BL (CI Acid Blue 80). The bath is run for 5 minutes, and the bath temperature iε

30 then raiεed to 212°at 3°F/min. After running the bath for 60 minuteε, the pH iε meaεured. If the pH iε >5.7, it is adjusted to 5.5 and run another 30 minuteε. The bath iε then cooled to 170°F, emptied, and cleared with clear water. Fabric is removed from the bath and dried.

35 The yarns in the fabrics were evaluated for LMDR as follows:

Fabric swatcheε (full width, i.e., approx-mately 60 inches wide and about 20-60 incheε long) were laid on a

large table covered with dull black plastic in a room with diffuse fluoreεcent lighting. The fabric iε rated by a panel of expertε (the ratings of 5 to 7 experts are averaged) on a scale from 1 to 10 as more further described below uεing the computerized εimulation of fabric εtreakε εhown in Figureε 23-32 aε a guide.

The εelected ratingε on the rating scale iε:

10 « no defect viεible, abεolutely uniform;

8 « minor unevenneεε obεerved but difficult to detect, acceptable for almoεt all end uses;

7 « superior;

6.5 ■ acceptable for very critical warp knit fabricε εuch aε thoεe uεed for εwimwear; 6 •*-= unevenneεε noticeable, uεable for oεt apparel; unacceptable except for εecond grade apparel;

4 - unevenneεε highly noticeable, too uneven for any apparel; and

2 « extremely uneven, disastrously defective; MBB Dyeability

For MBB dye testing a set of 42 yarn samples each sample weighing 1 gram iε prepared, preferably by jetting the yarn onto small dishes. 9 samples are for control; the remainder are for test.

All samples are then dyed by immersing them into 54 literε of an aqueouε dye εolution compriεed of 140 ml of a εtandard buffer εolution and 80 ml of 1.22% Anthraquinone Milling Blue BL (abbreviated MBB) (CI. Acid Blue 122). The final bath pH iε 5.1. The εolution temperature iε increaεed at 3-10°C/min. from room temperature to T _DΪE (dye tranεition temperature, which iε that temperature at which there iε a εharp increase in dye uptake rate) and held at that temperature for 3-5 minuteε. The dyed εampleε are rinεed, dried, and meaεured for dye depth by reflecting colorimeter.

The dye values are determined by computing K/S values from reflectance readings. The equations are:

K/S SAMPLE (1-R)2

MBB dyeability - K/S CONTROL X 180 AND K/S - 2R

when R - the reflectance value. The 180 value iε uεed to adjuεt and normalize the control εample dyeability to a known base. ABB Dyeability

A set of εampleε iε prepared in the εame manner aε for MBB Dyeability. All samples are then dyed by immersing them into 54 liters of an aqueouε dye εolution compriεed of 140 ml. of a εtandard buffer εolution, 100 ml of 10% Merpol LFH (a liquid, nonionic detergent from E. I. du Pont de Nemourε and Co.), and 80-500 ml of 0.56% ALIZARINE CYANINE BLUE SAP (abbreviated ABB) (CI. Acid Blue 45). The final bath pH is 5.9. The solution temperature is increased at 3-10°C/min from room temperature to 120°C, and held at that temperature for 3-5 minutes. The dyed samples are rinsed, dried, and measured for dye depth by reflecting colorimeter.

The dye values are determined by computing K/S values from reflectance readings. The equationε are:

K/S SAMPLE (1-R) ²

ABB dyeability - K/S CONTROL X 180 AND K/S - 2R

when R - the reflectance value. The 180 value iε uεed to adjust and normalize the control εample dyeability to

% CV of K/S meaεured on fabricε provideε an indication of LMDR. High LMDR correεpondε to low K/S valueε. Low % CV of K/S values iε deεirable.

Dye Transition Temperature is that temperature during dyeing at which the fiber structure openε up εufficiently to allow a εudden increaεe in the rate of dye

uptake. It is related to the polymer glasε tranεition temperature, to the thermomechanical hiεtory of the fiber, and to the εize and configuration of the dye molecule. Therefore it may be viewed aε an indirect meaεure of the "pore" εize of the fiber for a particular dye.

The dye tranεition temperature may be determined for CI. acid blue 122 dye aε followε: Preεcour yarn in a bath containing 800 g of bath per g of yarn sample. Add 0.5 g/1 of tetrasodium pyrophoεphate (TSPP) and 0.5 g/1 of Merpol(R) HCS. Raise bath temperature at a rate of 3°C/min. until the bath temperature iε 60°C Hold for 15 minutes at 60°C, then rinse. Note that the prescour temperature muεt not exceed the dye transition temperature of the fiber. If the dye tranεition temperature appearε to be cloεe to the εcour temperature, the procedure εhould be repeated at a lower εcour temperature. Set the bath at 30°C and add 1% on weight of fabric of CI. acid blue 122 and 5 g/1 of monobaεic εodium phosphate. Adjust pH to 5.0 using M.S.P. and acetic acid. Add yarn samples and raise bath temperature to 95°C at a rate of 3 ^β C/min.

With every 5°C rise in bath temperature take a dye liquor sample of "25 ml from the dye bath. Cool the samples to room temperature and measure the absorbance of each sample at the maximum abεorbance of about 633 nm on a εpectrophotometer using a water reference. Calculate the % dye exhaust and plot % dye exhaust vs dyebath temperature. Draw interεecting lineε along each of the two εtraight portionε of the curve and the intersection iε the dye tranεition temperature. To improve reproducibility of meaεurement it iε preferable to meaεure the dye tranεition temperature at 15% dye exhauεtion. The dye tranεition temperature (T _DYE ) iε a measure of the openness of the fiber structure and preferred values of T _DYE for warp drawn yarns are leεε than about 65°C, especially less than about 60 ^β C

The denier variation analyzer (DVA) is a

capacitance instrument, using the same principle as the Uster, for meaεuring along-end denier variation. The DVA meaεures the change in denier every 1/2 meter over a 240 meter sample length and reports %CV of these measurements. It alεo reportε % denier εpread, which iε the average of the high minus low readings for eight 30 meter sampleε. Meaεurementε in tableε uεing the DVA are reported aε coefficient of variation (DVA %CV) . Dynamic Mechanical Analyεiε tests are made according to the following procedure. A "Rheovibron" DDV-IIc equipped with an "Autovibron" computerization kit from Imasε, Inc., Hingham MA and an IMC-1 furnace, alεo from Imaεε, Inc., are uεed. Standard, stainless steel specimen support rods and fiber clamps, also from Imasε, Inc., are uεed. The computer program supplied with the Autovibron has been modified so that constant, selectable, heating rate and static tension on the specimen can be maintained over the temperature range -30 to 220 degrees C It haε also been modified to print the static tension, time and current specimen length whenever a data point is taken εo that the constancy of tension and heating rate can be confirmed and that shrinkage vs. temperature can be measured at constant stress. This computer program containε no correctionε for clamp maεs and load-cell compliance, and all operationε and calculationε, except as described above, are as provided by Imass with the Autovibron.

For tests on εpecimenε of this invention a static tension corresponding with 0.1 grams per denier (baεed on pre-teεt denier) iε uεed. A heating rate of 1.4 + 0.1 degrees C/minute is used and the teεt frequency iε 110 Hz. The computerization equipment makes one reading approximately every 1.5 minuteε, but this is not conεtant becauεe of variable time required for the computer to maintain the εtatic tenεion conεtant by adjustment of specimen length. The initial specimen length iε 2.0 + 0.1

cm. The test is run over the temperature range -30 to 230 degrees C Specimen denier iε adjuεted to 400 + 30 by plying or dividing the yarn to aεεure that dynamic and static forces are in the middle of the load cell range. The position (i.e., temperature) of tan delta and E" peaks iε determined by the following method. Firεt the approximate poεition of a peak iε eεtimated from a plot of the appropriate parameter vε. temperature. The final poεition of the peak iε determined by leaεt εquareε fitting a εecond order polynomial over a range of + 10-15 degreeε with respect to thiε eεtimated poεition conεidering temperature to be the independent variable. The peak temperature iε taken aε the temperature of the maximum of thiε polynomial. Tranεition temperatureε, i.e., the temperature of inflection pointε are determined similarly. The approximate inflection point iε eεtimated from a plot. Then εufficient data points to cover the transition from one apparent plateau to the other are fitted to a third order polynomial considering temperature to be the independent variable. The transition temperature iε taken aε the inflection point of the resulting polynomial. The E" peak temperature (T _E -„, _X ) around 100°C (see Figure 12) is taken aε the indicator of the alpha tranεition temperature (T _A ) and it iε important to have this a low value (i.e., less than 100 ^β C, preferably lesε than 95°C, especially lesε than 90 ^β C) for uniform dyeability.

Melting Behavior, including initial melt rate, is measured by a Differential Scanning Calorimeter (DSC) or a Differential Thermal Analyzer (DTA). Several inεtrumentε are εuitable for thiε meaεurement. One of theεe iε the Du Pont Thermal Analyzer made by E. I. Du Pont de Nemourε and Company of Wilmington, DE. Sampleε of 3.0 + 0.2 mg. are placed in aluminum capεuleε with capε and crimped in a crimping device all provided by the instrument manuf cturer. The sampleε are heated at a rate

of 20°C per minute for meaεurement of the melting point (T _M ) and a rate of 50°C per minute is.uεed to detect low temperature tranεitions which would normally would not be εeen becauεe of rapid recryεtallization during the heating of the yarn. Heating takes place under a nitrogen atmosphere (inlet flow of 43 ml/min. ) using glass bell jar cover provided by the instrument manufacturer. After the εample is melted the cooling exotherm iε determined by cooling the εample at 10°C per minute under the nitrogen atmoεphere. The melting point of nylon 66 homopolymer iε typically 260-262°C and iε lowered by about l ^β C/l% by weight of copolyadipamideε, such aε by addition of N6 and Me-5,6. The melting point of nylon 6 homopolymer iε typically 222°C (i.e., about 40°C lower than nylon 66) and may be raiεed by addition of higher melting point copolyamideε, εuch aε by addition of N66.

Interlace level of the polyamide yarn iε meaεured by the pin-insertion technique which, basically, involves insertion of a pin into a moving yarn and measureε yarn length (in cm.) between the point on the yarn at which the pin haε been inserted and a point on the yarn at which a predetermined force on the pin iε reached. For yarnε of >39 denier the predetermined force is 15 grams; for yarns of 39 denier the predetermined force iε

9 gramε. Twenty readingε are taken. For each length between pointε, the integer is retained, dropping the decimal, data of zero is dropped, and the log to the base

10 is taken of that integer and multiplied by 10. That result for each of the 20 readings is averaged and recorded as interlace level.

The amount of ε-caproamide monomer (N6% in Tables, herein) in 6-6 nylon iε determined aε followε: A weighed nylon εample is hydrolyzed (by refluxing in 6N HCI), then 4-aminobutyric acid is added as an internal standard. The εample iε dried and the carboxylic acid ends are methylated (with anhydrous methanolic 3N HCI),

and the amine ends are trifluoroacylated with trifluoroacetic anhydride/CH ₂ Cl ₂ at 1/1 volume ratio. After evaporation of solvent and exess reagentε, the reεidue is taken up in MeOH and chromatographed uεing a gas chromatograph εuch aε Hewlett Packard 5710A, commercially available from Hewlett Packard Co., Palo Alto, CA, with Flame ionization Detector, uεing for the column Supelco 6-foot x 4mm ID glaεε, packed with 10% SP2100 on 80/100 Supelcoport, commercially available from Supelco Co., Beliefonte, PA. Many gaε chromatographic inεtrumentε, columnε, and εupportε are εuitable for thiε meaεurement. The area ratio of the derivatized 6-aminocaproic acid peak to the derivatized 4-aminobutyric acid peak iε converted to mg 6 nylon by a calibration curve, and wt. % 6 nylon is then calculated.

The amount of Me5-6 in weight percent (reported as MPMD % in the Tables) is determined by heating two grams of the polymer, in flake, film, fiber, or other form (surface materialε such as finishes being removed) at 100°C overnight in a solution containing 20 mis of concentrated hydrochloric acid and 5 mis of water. The εolution iε then cooled to room temperature, adipic acid precipitateε out and may be removed. (If any Ti02 iε preεent it εhould be removed by filtering or centrifuging. ) One ml of thiε solution iε neutralized with one ml of 33% sodium hydroxide in water. One ml of acetonitrile is added to the neutralized solution and the mixture is shaken. Two phases form. The diamineε (MPMD AND HMD) are in the upper phaεe. One microliter of thiε upper phaεe is analyzed by Gas Chromatography such aε a capillary Gaε Chromatograph having a 30 meter DB-5 column (95% dimethylpolyεiloxane/5% diphenylpolyεiloxane) iε uεed although other columnε and εupportε are εuitable for thiε meaεurement. A εuitable temperature program iε 100°C for 4 minuteε then heating at a rate of 8°C/min up to 25π ^β c The diamineε elute from the column in about 5 minuteε, the

MPMD eluting firεt. The weight percentage MPMD is calculated from the ratio of the integrated areaε under the peaks for the MPMD and HMD and the weight percent _c Me5-6 is calculated from the weight percentage of the MPMD.

Draw Tenεion (DT ₃₃ ), expreεεed aε gramε per original denier, iε meaεured while drawing the yarn to be teεted while heating it. Thiε iε moεt conveniently done

10 by paεεing the yarn from a εet of nip rollε, rotating at approximately 180 meterε/minute εurface speed, through a cylindrical hot tube, at 185 + 2 ^β C (characteristic of the exit gain temperature in high speed texturing), having a 1.3 cm diameter, 1 meter long yarn passageway, then to a

15 second set of nip rollε, which rotate faεter than the firεt εet εo that the yarn iε drawn between the sets of nip rollε at a draw ratio of 1.33 X. A conventional tenεiometer placed between the hot tube and the firεt εet of nip rollε measures, yarn tension. The coefficient of

20 variation is determined εtatiεtically from replicate readings. Freεhly spun yarn is aged 24 hours before this meaεurement is done. Draw Tension e 1.05 Draw Ratio (DT 5%) is measured in the same manner except that draw ratio is 1.05X instead of 1.33X and hot tube temperature is at

25 135°C instead of 185 ^β C Using these settings, Average Secant Modulus (M ₅ ) iε calculated by the formula

([M _s /.denier]) x 100

30 5

(average valueε are denoted by bracketε)

% Coefficient of Variation of M ₅ iε also obtained in this manne . 35 Draw Tension @ 1.00 Draw Ratio (herein referred to as "along-end shrinkage tenεion") iε meaεured in the εame manner as DT 5% except that the draw ratio iε 1.00X and the hot tube temperature iε 75°C.

Draw Tenεion _ 1.20 Reεidual Draw Ratio (DT RPR = 1.2) is obtained in the same manner aε DT5 except that the draw ratio iε baεed on reεidual draw ratio of 1.20 X; i.e. ,

100 + E _B _ (in percent) Draw Ratio « 120

% of Coefficient of Variation iε alεo calculated uεing thiε data.

The Dynamic Shrinkage Tenεion (ST) iε meaεured uεing the Kanebo Streεε Teεter, model KE-2L, made by Kanebo Engineering, LTD., Oεaka, Japan, and distributed in the U.S. by Toyomenka America, Inc. of Charlotte, North Carolina. The tension in gramε iε meaεured versus temperature on a seven centimeter yarn sample tied into a loop and mounted between two loops under an initial preload of 5 milligramε per denier and heated at 30 degreeε centigrade per minute from room temperature to 260 degreeε centigrade. The maximum shrinkage tension (g/d) (Sτ _»« χ) and the temperature at S _TBax , denoted by T _STBax are recorded. Other thermal transitionε can be detected (εee detailed diεcuεεion of Figure 10).

The Dynamic Length Change (ΔL) of a yarn under a pretenεioning load verεuε increasing temperature (ΔT) is measured using the Du Pont Thermomechanical Analyzer (TMA), model 2940, available from the E. I. Du Pont de Nemours and Co., Inc. of Wilmington, Delaware. The change in yarn length (ΔL, %) versuε temperature (degreeε centigrade) iε meaεured on a 12.5 milimeter length of yarn which iε: 1) mounted carefully between two press-fit aluminum balls while keeping all individual filaments straight and unstreεεed with the cut filament endε fuεed outεide of the ball mountε uεing a micro εoldering device to avoid slippage of individual filaments; 2) pre-εtreεsed to an initial load of 5 mg/denier for meaεurement of

shrinkage and to 300 mg/denier for measurement of extension; and 3) heated from room temperature to 300 degrees centigrade at 50 degreeε per minute with the yarn length at 35 degreeε centigrade defined aε the initial length. The change in length (ΔL, %) is measured every two seconds (i.e., every 1.7 degreeε) and recorded digitally and then plotted verεuε specimen temperature. An average relationship iε defined from at leaεt three repreεentative plotε. Preferred draw feed yarnε have a negative length change (i.e, the yarnε εhrink) under a 5 mg/d tenεion over the temperature range of 40°C to 135 ^β C

The inεtantaneouε change in length verεuε temperature (ΔL,%)/(ΔT, °C), herein called the Dynamic Shrinkage Rate under shrinkage conditionε (5 mg/d) and the Dynamic Extenεion Rate under extenεion conditionε (300 mg/d), iε derived from the original data by a floating average computation and replotted versus specimen temperature. Preferred draw feed yarns have a negative dynamic εhrinkage rate (i.e., the yarnε do not elongate after initially shrinking) over the temperature range on 40°C to 135°C Under extension condtions (300 mg/d pre-tenεion load), the value of (ΔL/ΔT) iε found to increaεe with increaεing temperature, reaching an intermediate maximum value at about 110-140 ^β C, decreaεing εlightly in value at about 160-200°C and then increasing in value sharply as the yarn begins to soften prior to melting (see Figure 7). The intermediate maximum in (ΔL/Δ T), occuring between about 110 ^β C-140°C, is herein called (ΔL/ΔT)max and iε taken aε a meaεure of the mobility of the polymer network under εtreεε and high temperatureε. Preferred draw feed yarnε have a (ΔL/ΔT)max value, aε meaεured at 300 mg/d, of leεs than about 0.2 (%/°C), preferably lesε than about 0.15 (%/°C) and greater than about 0.05 %/°C

Another important characteriεtic of a polymer network iε the εensitivity of itε (ΔL/ΔT)max value with

increasing εtreεε which is defined as the tangent to the plot of (ΔL/ΔT)max versuε σ _D at a σ _D -value of 300 mg/d (denoted by d(ΔL/ΔT) _MAX /dσ _D ) and determined on separate specimens pre-streεεed from 3 mg/d to 500 mg/d (see figureε 5 and 6). A 300 mg/d εtreεε value iε εelected for characterization since it approximates the nominal streεε level in the draw relaxation zone (i.e., between rollε 17 and 18 in Figure 2). The Hot Draw Streεε ( σ _D ) vs. Draw Ratio Curve iε uεed to εimulate the reεponεe of a draw feed yarn to increaεing draw ratio (DR) and draw temperature (T _D ). The draw εtreεε ( σ _D ) iε measured the same as DT ₃₃ %, except that the yarn speed iε reduced to 50 meters per minute, the meaεurement is taken over a length of 100 meters, and different temperatures and draw ratios are used as deεcribed herein. The draw εtreεε (σ _D ) is expressed aε grams per drawn denier (g/dd); that is, σ _D - DT(g/d) x DR, and is plotted versuε draw ratio (DR) at 75°C, 125 °C, and 175°C (εee Figure 20). The draw stress (σ _D ) , increases linearly with draw ratio for values of DR greater than about 1.05 (i.e., above the yield point) to the onset of strain-hardening (i.e., to a reεidual draw ratio (RDR) _D of about 1.25), and the slope of best fit linear plot of draw streεε verεuε draw ratio iε herein called the draw moduluε (M _D - Δσ _D /ΔDR) . The valueε of draw stress ( _Ό ) and draw modulus (M _D ) decrease with increasing draw temperature (T _D ). The desired level of draw streεε (σ„ ) and draw moduluε (M _D ) can be controlled by selection of feed yarn type and draw temperature (T _D ). Preferred draw feed yarns have a draw streεs (σ _D ) between about 1.0 and about 2.0 g/dd, and a draw moduluε (M _D ) between about 3 to about 7 g/dd, as measured at 75°C and at a 1.35 draw ratio (DR) taken from a best fit linear plot of draw streεε ( σ _D ) verεuε draw ratio (εee Figureε 20 and 21). The temperature of 75°C is εelected εince it iε found that moεt nylon εpin-oriented feed yarnε have reached their

maximum shrinkage tension and have not yet begun to undergo significant recryεtallization (i.e. , thiε iε more indicative of the mechanical nature of the "as-spun" _c polymer chain network above its glass transition temperature, T _g , before the network haε been modified by thermal recryεtallization).

Apparent Draw Energy (E _D ) _a , iε the rate of decreaεe of the draw moduluε with increasing temperature

10 (75°C, 125°C, 175°C) and is defined as the εlope of a plot of the logarithm of the draw moduluε, ln(M _D ), versuε [1000/(T _D ,°C + 273)], aεεuming an Arrheniuε type temperature dependence (i.e., M _D - Aexp(E _D /RT) , where T iε temperature in degreeε Kelvin, R iε the univerεal gaε 5 conεtant, and "A" iε a material conεtant). Preferred draw feed yarnε have an apparent draw energy (E _D ) _a [» E _D /R - Δ(lnM„ )/Δ(1000/T _D ) , where T„ iε in degreeε Kelvin] about 0.2 to about 0.6 (g/dd)/°K.

The Differential Dye Variance iε a measure of 0 the along-end dye uniformity of a warp drawn yarn and iε defined by the difference in the variance of K/S measured in the axial and radial directions, respectively, on a lawson knit sock dyed according to the MBB dye procedures described herein. The LMDR of a warp knit fabric is found 5 to vary inverεely with the warp drawn yarn Differential Dye Variance (axial K/S variance - radial K/S variance). The warp draw proceεε of the invention balanceε the draw temperature, extent of draw, relaxation temperature, and

30 extent of relaxation so to minimize the Differential Dye Variance (DDV) of the warp drawn yarn product.

Tensionε expreεεed in termε of gramε per drawn denier (g/dd) (herein εometimeε referred to as "streεε") may be meaεured by uεe of the Rothεchild Electronic

35 Tenεiometer. Model R-1192A operation conditionε are: 0 to 100 gram head; range *•= 25 (scale 0 to 40 grams on diεplay); calibrated with Lawεon-Hemphill Tenεiometev Calibration Device are commercially available from:

Lawεon-Hemphill Sales, Inc., PO Drawer 6388, Spartanεburg, SC

Along-end Shrinkage of yarnε may be meaεured by

,. the Lawεon-Hemphill Texured Yarn Teεt εyεtem (TYT) aε follows: A suitable Tester is the Model 30 available from Lawson-Hemphill Saleε, Inc., P. 0. Drawer 6388, Spartanεburg, SC. Four yarn length meaεurementε are made in the εequence: (Li); (2) length under juεt enough

10 tenεion to εtraighten the yarn (L ₂ ); (3) length upon heating to further develop εhrinkage under very low tenεion L ₃ ) ; (4) and the final yarn length (L ₄ ) under juεt enough tenεion to εtraighten the yarn. Shrinkage iε calculated by the formula:

I ⁵ L ₂ - L ₄

Shrinkage (%) - L ₂ ^~~ X 100

Amine (NH2) and Carboxyl (COOH) endε are determined by the methodε described on pages 293 and 294 in Volume 17 of the "Encyclopedia of Industrial Chemical

20 Analyεis" published by John Wiley & Sons, Inc. in 1973, and are expressed in terms of equivalents per 10 ⁶ gramε. Typical nylon 66 polymer haε about 30-50 equivalentε of NH2-endε and "deep" dye nylon 66 polymer haε about 50-70 equivalentε of NH2-endε. The number average molecular

25 weight (M _H ) iε approximately proportional to the reciprocal of the total number of NH2 and COOH endε, expreεεed aε equivalentε per 10 ⁶ gramε; that iε, M _N - 2xl0 ⁶ iε εtill in (NH2 + COOH + SE), where SE is the

30 number of equivalent stabilized non-reactive end groupε. For example, nylon 66 polymer having a M„ of about 15,000 has a RV of about 44 and a total number of endε of about 133; and for example, nylon 66 polymer having a M _N of about 20,000 has a RV of about 66 and a total number of 35 ends of about 100; wherein for nylon 66 polymer the M _N and RV are approximately inter-related by the expression M _N - 1065(RV)° • ⁷ ; and for nylon 6 polymers the expreεεion M _N = 1002(RV) ⁰ - ⁷⁴ may be uεed. Polyamide polymerε of about 50

to about 80 RV with about 30 to about 70 equivalent NH2-ends are preferred.

Density( p) of the polyamide fiber is measured by _c use of the standard density gradient column technique using carbon tetrachloride and heptane liquids at 25°C

The Fractional Volume Crystallinity (Xv) iε calculated from the fiber denεity (p) measurement using the following formula: X _v - ( p-p, )/( p _c -ρ _« ) ; where, p _c iε

10 the denεity of the perfectly cryεtalline phaεe and p, iε the density of the amorphous phase. For nylon 66, ρ _c - 1.22 g/cm ³ and p, ■ 1.069 g/cm ³ [H. W. Starkweather, Jr., R. E. Moynihan, Journal of Polymer Science, vol. 22, p. 363 (1956)]. The Fractional Weight Crystallinity (Xw) and

15 the fractional volume crystallinity (Xv) are related by the formula: Xw - Xv ( p/p _c ) . The fractional volume crystallinity varieε only εlightly with warp draw proceεs conditionε, e.g., typically varying from about 0.5 to about 0.55.

20 The Optical Parameterε of the fiberε are meaεured according to the method described in Frankfort and Knox U.S. Patent No. 4,134,882, beginning at column 9, line 59 and ending at column 10, line 65 with the following exceptions and additions. First instead of

25 Polaroid T-410 film and 1000X image magnification, high speed 35mm film intended for recording oscilloscope traces and 300X magnification are uεed to record the interference patternε. Alεo εuitable electronic image analysis methods

30 which give the same result can be used. Second, the word "than" in column 10, line 26 iε replaced by the word "and" to correct a typographical error. Becauεe the fiberε of thiε invention are different from thoεe of 4,134,882, additional parameterε, calculated from the εame n|| and n_|_

35 diεtributionε at +.05. Here the + referε to oppoεite sideε from the center of the fiber image. The iεotropic refractive index (RISO) at +.05 iε determined from the relationεhip:

RISO ( . 05 ) - [ ( n | | ) ( . 05 ) +2 ( nJ_) ( . 05 ) ) ]/3

Finally the average value of any of the optical parameterε iε defined aε the average of the two valueε at +.05, e.g.:

<RISO> « (RISO(.05) + RISO(-.05) )/2,

and εimilarly for the Average Birefringence (Δn). The average birefringence (Δn) may in turn be expressed aε the εum of the crystalline (Δc) and amorphouε (Δa) birefringenceε: Δn « Δc + Δa; where, Δc » Δc ^β fcXv and Δa = Δa°fa(l-Xv) and Δc°,a° are the intrinεic birefringenceε of the cryεtalline and .amorphouε regionε, reεpectively, with valueε of 0.073 [M. F. Culpin, and K. W. Kemp, Proc. Physicε Society, vol. 69C, p. 1301 (1956)]; fc,a are the orientation functionε of the crystalline and amorphouε regionε, reεpectively; and Xv and (1-Xv) are the fractional volumeε of the crystalline and amorphouε regionε, reεpectively. The value of the Crystalline Orientation Function (fc) is defined by the expression: fc « l-OA/180, where OA is the crystalline orientation angle, defined hereinafter; permitting the Amorphous Orientation Function (fa) to be calculated from the formula: fa - (Δn - Δc ^β fcXv)/Δa°(l-Xv) and an Average Orientation Function (favg) to be calculated from the formula: favg ■» (Δn)/0.073. [R. S. Stein, Journal Polymer Science, Vol. 21, pgs 381-396 (1956)].

Cryεtal Perfection Index (CPI) and Apparent Cryεtallite Size: Crystal perfection index and apparent crystallite size are derived from X-ray diffraction εcans. The diffraction pattern of fibers of these compositions is characterized by two prominent equatorial X-ray reflections with peaks occurring at scattering angle (2Θ) approximately 20°-21° and 23°.

X-ray diffraction patternε of theεe fiberε are

obtained with an X-ray diffractometer (Philips Electronic Instruments, Mahwah, N.J., cat. no. PW1075/00) in reflection mode, using a diffracted-beam mono-chromator c and a scintillation detector. Intensity data are measured with a rate meter and recorded by a computerized data collection/reduction εyεtem. Diffraction patternε are obtained uεing the inεtrumental εettingε:

Scanning Speed 1° 26 per minute; 10 Stepping Increment 0.025° 2θ;

Scan Range 6° to 38°, 2Θ; and

Pulεe Height Analyzer, "Differential". For both Cryεtal Perfection index and Apparent Cryεtallite Size meaεurementε, the diffraction data are processed by a 15 computer program that smootheε the data, determines the baseline, and measureε peak locationε and heightε.

The X-ray diffraction measurement of crystallinity in 66 nylon, 6 nylon, and copolymerε of 66 and 6 nylon iε the Cryεtal Perfection Index (CPI) (aε 0 taught by P. F. Dismore and w. 0. Statton, J. Polym. Sci. Part C, No. 13, pp. 133-148, 1966). The positionε of the two peakε at 21° and 23° 26 are observed to shift, and as the crystallinity increases, the peaks shift farther apart and approach the positions corresponding to the "ideal" 5 positionε baεed on the Bunn-Garner 66 nylon structure. This shift in peak location provides the baεiε of the measurement of Crystal Perfection Index in 66 nylon:

30 [d(outer)/d(inner)] - 1

CPI - X 100

0.189

where d(outer) and d(inner) are the Bragg 'd' spacingε for 5 the peaks at 23° and 21° respectively, and the denominator 0.189 is the value for d(100)/d(010) for well-crystallized 66 nylon as reported by Bunn and Garner (Proc. Roya] Soc. (London) , A189, 39, 1947). An equivalent and more

uεeful equation, baεed on 2θ valueε, iε:

CPI = [2θ(outer)/2θ(inner) - 1] X 546.7

Apparent Cryεtallite Size: Apparent cryεtallite εize iε calculated from meaεurementε of the half-height peak width of the equatorial diffraction peakε. Becauεe the two equatorial peakε overlap, the measurement of the half-height peak width iε baεed on the half-width at half-height. For the 20°-21 ^β peak, the poεition of the half-maximum peak height iε calculated and the 26 value for thiε intenεity is meaεured on the low angle εide. The difference between thiε 26 value and the 26 value at maximum peak height iε multiplied by two to give the half-height peak (or "line") width. For the 23° peak, the poεition of the half-maximum peak height iε calculated and the 26 value for this intenεity iε meaεured on the high angle εide; the difference between thiε 26 value and the 26 value at maximum peak height is multiplied by two to give the half-height peak width.

In thiε meaεurement, correction is made only for instrumental broadening; all other broadening effects are assumed to be a result of crystallite size. If 'B' iε the meaεured line width of the sample, the corrected line width 'beta' is

( _B 2 -b2 )i/2

where 'b' is the instrumental broadening constant. 'b' iε determined by meaεuring the line width of the peak located at approximately 28° 26 in the diffraction pattern of a εilicon cryεtal powder εample. The Apparent Cryεtallite Size (ACS) is given by

ACS = (Kλ)/(β cos 6), wherein

K iε taken aε one (unity); λ iε the X-ray wavelength (here 1.5418A); 0 is the corrected line breadth in radians; and θ is half the Bragg angle (half of the 26 value of the εelected peak, aε obtained from the diffraction pattern). The ACS for the "outer" and "inner" d-εpacingε are alεo referred to aε ACS(IOO) and ACS(OIO), reεpectively. An Apparent Cryεtallite Volume (ACV) iε herein defined by the expreεεion: ACV - [ACS(100)*ACS(010) ] ³ / ² , 3.

X-ray Orientation Angle: A bundle of filamentε about 0.5 mm in diameter iε wrapped on a sample holder with care to keep the filaments essentially parallel. The filamentε in the filled εample holder are exposed to an x-ray beam produced by a Philips x-ray generator (Model 12045B) available from Philipε Electronic Instruments. The diffraction pattern from the sample filaments iε recorded on Kodak DEF Diagnoεtic Direct Exposure X-ray film (Catalogue Number 154-2463), in a Warhus pinhole camera. Collimators in the camera are 0.64 mm in diameter. The expoεure iε continued for about fifteen to thirty minuteε (or generally long enough so that the diffraction feature to be measured iε recorded at an Optical Denεity of ~1.0). A digitized image of the diffraction pattern iε recorded with a video camera. Tranεmitted intenεitieε are calibrated using black and white references, and gray level (0-255) is converted into optical density. The diffraction pattern of 66 nylon, 6 nylon, and copolymers of 66 and 6 nylon haε two prominent equatorial reflectionε at 26 approximately 20°-21° and 23°; the outer (-23°) reflection iε uεed for the measurement of Orientation Angle. A data array equivalent to an azimuthal trace through the two selected equatorial peaks (i.e. the outer reflection on each side of the pattern) iε created by interpolation from the digital image data file; the array is constructed so that one data point equalε one-third of one degree in arc.

The Orientation Angle (OA) is taken to be the arc length in degrees at the half-maximum optical density (angle subtending points of 50 percent of maximum density) of the equatorial peaks, corrected for back-ground. Thiε is computed from the number of data pointε between the half-height points on each εide of the peak (with interpolation being uεed, thiε iε not an integral number). Both peakε are meaεured and the Orientation Angle iε taken as the average of the two measurements.

Long Period Spacing and Normalized Long Period Intensity: The long period spacing (LPS), and long period intensity (LPI), are meaεured with a Kratky small angle diffractometer manufactured by Anton Paar K.G., Graz, Auεtria. The diffractometer iε inεtalled at a line-focus port of a Philipε XRG3100 x-ray generator equipped with a long fine focuε X-ray tube operated at 45KV and 40ma. The X-ray focal εpot iε viewed at a 6 degree take-off angle and the beam width iε defined with a 120 micrometer entrance εlit. The copper K-alpha radiation from the X-ray tube iε filtered with a 0.7 mil nickel filter and iε detected with a NaΙ(TI) Scintillation counter equipped with a pulεe height analyzer εet to pass 90% of the CuK-alpha radiation symmetrically.

The nylon sampleε are prepared by winding the fiberε parallel to each other about a holder containing a 2 cm diameter hole. The area covered by the fiberε iε about 2 cm by 2.5 cm and a typical sample contains about 1 gram of nylon. The actual amount of sample iε determined by meaεuring the attenuation by the sample of a strong CuK-alpha x-ray signal and adjuεting the thickneεε of the εample until the tranεmiεεion of the X-ray beam iε near 1/e or .3678. To meaεure the transmisεion, a εtrong εcatterer iε put in the diffracting poεition and the nylon εample is inserted in front of it, immediately beyond the beam defining slits. If the measured intenεity without attenuation iε Io and the attenuated intenεity iε I, then

the tranεmiεεion T iε I/(Io). A εample with a tranεmission of 1/e haε an optimum thickneεε εince the diffracted intensity from a sample of greater or leεε _c thickneεε than optimum will be leεε than that from a εample of optimum thickneεs.

The nylon sample is mounted such that the fiber axiε iε perpendicular to the beam length (or parallel to the direction of travel of the detector). For a Kratky

10 diffractometer viewing a horizontal line focuε, the fiber axiε iε perpendicular to the table top. A εcan of 180 pointε iε collected between 0.1 and 4.0 degreeε 26, aε follows: 81 pointε with εtep εize 0.0125 degreeε between 0.1 and 1.1 degreeε; 80 pointε with εtep εize 0.025

15 degreeε between 1.1 and 3.1 degreeε; 19 pointε with εtep εize 0.05 degreeε between 3.1 and 4.0 degrees. The time for each scan iε 1 hour and the counting time for each point is 20 secondε. The reεulting data are smoothed with a moving parabolic window and the instrumental background

20 is subtracted. The inεtrumental background, i.e. the εcan obtained in the abεence of a sample, is multiplied by the transmission, T, and subtracted, point by point, from the scan obtained from the sample. The data pointε of the εcan are then corrected for sample thickness by

25 multiplying by a correction factor, CF - -1.0/(eT ln(T)). Here e is the base of the natural logarithm and ln(T) iε the natural logarithm of T. Since T iε leεε than 1, ln(T) iε always negative and CF is positive. Also, if τ«l/e,

30 then CF-1 for the sample of optimum thickness. Therefore, CF is always greater than 1 and correctε the intenεity from a εample of other than optimum thickneεε to the intenεity that would have been observed had the thickneεε been optimum. For εample thicknesseε reaεonably cloεe to

35 optimum, CF can generally be maintained to lesε than 1.01 εo that the correction for εample thickneεε can be maintained to leεε than a percent which iε within th*- uncertainty impoεed by the counting εtatiεtics.

The meaεured intenεitieε ariεe from reflections whose diffraction vectors are parallel to the fiber axis. For most nylon fibers, a reflection iε obεerved in the vicinity of 1 degree 26. To determine the preciεe position and intenεity of thiε reflection, a background line iε firεt drawn underneath the peak, tangent to the diffraction curve at angleε both higher and lower than the peak itεelf. A line parallel to the tangent background line iε then drawn tangent to the peak near itε apparent maximum but generally at a slightly higher 26 value. The 26 value at this point of tangency iε taken to be the poεition εince it iε poεition of the maximum if the εample back-ground were εubtracted. The long period εpacing, LPS, iε calculated from the Bragg Law uεing the peak poεition thuε derived. For εmall angleε thiε reduceε to:

LPS - λ/εin(2θ)

The intenεity of the peak, LPI, iε defined aε the vertical diεtance, in countε per second, between the point of tangency of the curve and the background line beneath it.

The Kratky diffractometer is a εingle beam inεtrument and meaεured intensities are arbitrary until standardized. The measured intensities may vary from instrument to inεtrument and with time for a given inεtrument because of x-ray tube aging, variation in alignment, drift, and deterioration of the scintillation cryεtal. For quantitative comparison among samples, meaεured intenεitieε were normalized by ratioing with a εtable, εtandard reference εample. Thiε reference waε choεen to be a nylon 66 εample (T-717 yarn from E. I. du Pont Co., Wilmington, De.) which was uεed aε feed yarn in the firεt example of thiε patent (Feed yarn 1).

Sonic Modulus: Sonic Moduluε iε meaεured aε reported in Pacofεky U.S. Patent No. 3,748,844 at col. 5, lineε 17 to 38, the disclosure of which is incorporated by

reference except that the fibers are conditioned for 24 hours at 70°F (21 °C) and 65% relative, humidity prior to the test and the nylon fibers are run at a tension of 0.1 grams per denier rather than the 0.5-0.7 reported for the polyester fibers of the referenced patent.

Preferred drawn yarnε have sonic moduluε (Mε) values between about 40 and 60 g/d, and especially between about 40 and 55 g/d. Crosε Polarization combined with "magic angle εpinning" (CP/MAS) are Nuclear Magnetic Resonance (NMR) techniques uεed to collect spectral data which describe differences between the copolymer and homopolymer in both structure and composition. In particular solid state carbon-13 (C-13) and nitrogen-15(N-15) NMR data obtained using CP/MAS can be uεed to examine contributions from both crystalline and amorphouε phases of the polymer. Such techniques are deεcribed by Schafer et. al. in Macromolecules 10, 384 (1977) and Schaefer et. al. in J. Magnetic Reεonance 34, 443 (1979) and more recently by Veeman and coauthorε in Macromolecules 22, 706(1989).

Structural information concerning the amorphouε phaseε of the polymer is obtained by techniques described by Veeman in the above mentioned article and by VanderHart in Macromolecules 12, 1232 (1979) and Macromolecules 18, 1663 (1985).

Parameterε governing molecular motion are obtained by a variety of techniqueε which include C-13 Tl and C-13 Tlrho. The C-13 Tl waε developed by Torchia and deεcribed in J. Magnetic Reεonance, vol. 30, 613 (1978). The meaεurement of C-13 Tlrho iε deεcribed by Schafer in Macromolecules 10, 384 (1977).

Natural abundance nitrogen-15 NMR iε used to provide complementary information in addition to that obtained from carbon-13 solid state NMR analysiε. Thiε analyεiε alεo provideε information on the diεtribution of cryεtal εtructureε with the polymer aε illustrated by

Mathias in Polymer Commun. 29, 192 (1988). Dye rate methods:

It is well known that the dye rate of nylon fibers iε strongly dependent on the structure. The radial and axial diffusion coefficients of dyes in nylon fiberε may be meaεured according to the procedureε deεcribed in Textile Reεearch Inεtitute of Princeton, N.J., in Dye Transport Phenomena, Progresε Report No. 15 and referenceε therein.

The loεε of dye from a dye bath and thuε sorption of the dye by the fiber and calculation of a diffusion coefficient from the data may be carried out uεing the procedureε deεcribed by H. Kobεa in a εerieε of articles in Textile Reεearch Journal, Vol. 55, No. 10,

October 1985 beginning at page 573. A variation of thiε method iε available at the Hamby Textile Inεtitute of Carey, N.C; wherein the dye rate, (S ₂₅ ) expressed in units of reciprocal seconds (sec- ¹ ), is measured uεing CI. Acid Blue 40 at 25°C An Apparent Diffusion Coefficient (D _A ), which characterizes the "porosity" of the fiber structure to dye uptake, iε defined herein by the expreεεion: D _A (cm ₂ /εec) - Measured Dye Rate (S ₂₅ ) x Average Filament Cross-sectional Area (cm ² )-Ϊ_ Filament Shape Factor, wherein the Average Filament Cross-sectional Area is defined in terms of the filament denier and density by the relationεhip: Area (cm∑ ) - (dpf/denεity)/(9xl0 ⁵ ) and where, the Filament Shape Factor iε defined by [l/4π) x εquare of the filament circumference divided by the filament croεε-sectional area]; that is, the Apparent Diffusion Coefficient (D _A ) is defined herein by the expreεεion:

A 3 dpf ro having a measured dye rate of 50x10- ⁵ sec- ¹ has a calculated apparent diffusion coefficient (D _A ) of 14.6xl0- ¹⁰

cm ² εec- ¹ . Preferred filamentε have an apparent diffuεion coefficient (D _A ) of at leaεt about 15x10- ¹⁰ cm εec- ¹ and eεpecially preferred have an apparent diffuεion coefficient (D _A of at leaεt about 20x10- ^l ° cm ² εec- .

Apparent Pore Mobility (APM) and Apparent Pore Volume (APV) are meaεureε of the openneεε of the amorphouε regionε to permit εufficient dye uptake for uniform along-end dyeing. The Apparent Pore Mobility (APM) iε defined by the expreεεion: (l-fa)/fa - (1/fa -1). [A.

Peterlin, J. Macromol. Sci. B, Vol. 11, p. 57 (1975).] and the Apparent Pore Volume (APV) iε defined by the expreεεion: (CPI/100)ACV which iε analogouε to the expreεεion for amorphouε free-volume per cryεtallite uεed for polyeεter fiberε [J. H. Dumbleton and T. Murayama,

Kolloid-Z., Z. Polym., Vol 220, No. 1, p. 41 (1967)]. To achieve uniform dyeings with Large Molecule Dyes, such as with Cl. Acid Blue 122, the drawn yarns preferably have an APM greater than about 2 and greater than about [4.75-(0.37xlO-< )APV] and an APV greater than about 4xl0 ⁴ cubic angεtromε; and preferred drawn yarnε have an APM greater than about 2 and greater than about [5-(0.37x10- )APV] and an APV greater than about 4xl0 ⁴ cubic angstroms (as illustrated in Figure 26.

EXAMPLE I

Parts A-E illustrate the poor fabric appearance after dying of fabrics knit from nylon flat yarns produced by warp-drawing and relaxing of feed yarns spun at low withdrawal speeds. These yarns, which are unsatisfactory for critical dye applications, are believed to result in poor fabric appearance because of along-end variations in dye uptake which are worse than fully-drawn yarnε produced by a conventional εpin-draw proceεε. Partε F-K illuεtrate the proceεε of the invention and the εuperior LMDR values obtainable using yarns produced in accordance with the invention.

Part A - Comparative

Nylon 6 having an RV of ~46 iε εpun at a melt temperature of 270°C through a εpinneret having 13 capillarieε of length 0.022" and diameter 0.015". A quench cabinet iε εupplied with a croεε-flow of 20°C quench air at an average velocity of ~67 feet per minute (fpm). It is spun using a very low withdrawal εpeed of 590 mpm and iε not mechanically drawn during the εpinning process. Thiε yarn can be referred to as a "low orientation yarn" (LOY). Finish is applied after converging of the filamentε but no interlace is applied. The resulting 134 denier yarn haε a very low orientation making it unεuitable for knitting or weaving aε evidenced by a high elongation of about 320%. 670 bobbinε of the feed yarn are placed on a creel equipped with tenεioning deviceε for use in making yarn for 21" wide tricot. The creel and tensioning deviceε are the εame aε those commonly used for preparing beams of yarn. The ends of yarn are passed through reeds and guides designed to arrange the yarns in a parallel manner to form a warp, and are then passed to a Barmag STFl draw unit at a warp draw ratio of 3.00, a draw roll temperature of 60°C, an overfeed of 2.5%, a relaxation temperature of 22°C, and wound onto a beam at a speed of 320 mpm. The resulting yarn has a denier of 44.2 and an elongation of 52.8%.

Beamε of the drawn yarn are knit into a 32 gauge tricot fabric and dyed with C I. Acid Blue 80 dye according to the LMDR procedure. The dyed fabric iε rated for uniformity and unacceptable LMDR of 4 iε achieved. Detailε of the proceεε and yarn propertieε are provided in Table 1.

Part B - Comparative Nylon 66 having an RV of ~40 iε spun at a melt temperature of 290°C through a spinneret containing 14 capillaries of length 0.022" and diameter 0.015". The filaments are quenched and converged aε in Part A to

produce a 125 denier feed yarn having propertieε aε described in Table I. 670 bobbins of the feed yarn are drawn at 500 mpm using a Karl Mayer DSST 50 machine aε indicated in Table I to produce a 44 denier yarn with the propertieε liεted in Table I. When dyed with C. I. Acid Blue 80 dye aε in Part A, the LMDR is an unacceptable 3.5

Part C - Comparative Nylon 6,6 having an RV of "42 is spun at a melt temperature of 290°C through a εpinneret having 13 capillarieε of length 0.022" and diameter 0.015". A quench cabinet iε supplied with a cross-flow of 20 ^β C quench air at an average velocity of ~67 feet per minute (fpm). The filaments are converged into yarn at a finiεh roll applicator juεt below the quench cabinet. The yarn iε then paεεed through an interfloor tube to a feed roll which provideε a withdrawal speed of 1500 mpm and then to a draw roll at a speed 1.60 times that of the feed roll or 2400 mpm. Subsequent rolls may vary the speed slightly from 2400 mpm to adjust tensions. Interlace was applied at a level sufficient for efficient removal of the yarn later from the bobbin. The yarn is wound on a tube at a tension of ~ 0.2 g/d. Thiε yarn, having been mechanically drawn only 1.60X, iε at this point only partially oriented and does not yet possess the tensile propertieε ideal for warp knitting or weaving and is used aε the feed yarn for the warp draw operation described before. It has a denier of 55 and an elongation of ~80% and can be referred to aε a partially drawn yarn (PDY).

The feed yarn iε warp drawn on a Barmag model STFl draw unit at a draw ratio of 1.39X, a draw temperature of 60°C, an overfeed of 5%, a relaxation temperature of 120°C and wound into a beam at a εpeed of 500 mpm. The reεulting yarn haε a denier of 42 and an elongation of 30%.

The drawn yarn iε knit into a tricot fabric, dyed with C.I. Acid Blue 122 dye, and rated for LMDR.

The LMDR iε an unacceptable 4.4. Detailε of the proceεε and yarn propertieε are provided in Table 1.

Part D - Comparative The feed yarn iε prepared aε deεcribed in Part C except that the RV iε 44, the feed roll (withdrawal) εpeed iε 1849 mpm, the wind-up εpeed iε 3217 mpm, and the draw ratio iε 1.74X. The feed yarn in thiε example is 53 denier/13 filaments, has an elongation of 74% and a draw tenεion of 58 g.

The feed yarn iε warp drawn on the Karl Mayer DSST 50 unit at a draw ratio of 1.35X, and a draw roll temperature of 70 ^β C The drawn yarn is overfed by 5% to the exit rolls, relaxed at 129 ^β C between the draw rollε and the exit rollε, and wound into a beam at 500 mpm. The reεulting PDY yarn haε a denier of 41 and an elongation of ~40%.

Beamε of the warp drawn yarn are knitted on a 32 gauge tricot knitting machine to form a warp knit fabric. The fabric is dyed using CI. Acid Blue 80 dye and rated for LMDR uniformity. An unacceptable LMDR of 3 iε obtained. Details of the process and yarn properties are provided in Table 1.

Part E - Comparative The feed yarn is prepared as described in Part C except that the RV is 45, the feed roll (withdrawal) speed iε 1937 mpm, the wind-up speed is 3254 mpm, and the draw ratio is 1.68X. The feed yarn in thiε example iε 95 denier/34 filamentε, haε an elongation of 67% and other propertieε aε indicated in Table I.

The feed yarn iε warp drawn on the Barmag model STFl unit at a draw ratio of 1.43X, and a draw roll temperature of 60°C The drawn yarn iε overfed by 5% to the exit rollε, relaxed at 22°C between the draw rollε and the exit rollε, and wound into a beam 500 mpm. The reεulting PDY yarn haε a denier of 72.7 and an elongation of "34.2%.

Beamε of the warp drawn yarn are knitted on a 32 gauge tricot knitting machine to form a warp knit fabric. The fabric iε dyed uεing Cl. Acid Blue 80 dye and rated for LMDR uniformity. An unacceptable LMDR of 3 iε obtained. Detailε of the proceεε and yarn propertieε are provided in Table 1.

Part F - Invention Nylon 6,6 having an RV of ~42 iε spun at a melt temperature of 290°C through a spinneret containing 17 capillarieε of length 0.022" and diameter 0.015". A quench cabinet is supplied with a croεε-flow of 20 ^β C quench air at an average velocity of ~67 fpm. The filamentε are converged into yarn at a finiεh roll applicator juεt below the quench unit. The yarn iε then paεεed through an interfloor tube to a feed roll which provideε a withdrawal speed of 2818 mpm and then to a draw roll at a speed 1.26 timeε that of the feed roll or 3551 mpm. Subεequent rollε may vary the speed slightly from 3551 mpm to adjust tenεionε and apply interlace. The yarn iε wound on a tube at about 3551 and at a tenεion of ~ 0.2 gpd. The result is a 55 denier PDY yarn with an elongation of 60% and a draw tension of 59 g.

The yarn iε warp drawn on the Barmag STFl draw unit at a draw ratio of 1.29, a draw temperature of 60°C, an overfeed of 6%, waε relaxed at 22°C and wound into a beam at a speed of 550 mpm. The resulting yarn had a denier of 45.5 and an elongation of 28.5%. The drawn yarn iε knit into a tricot fabric, dyed with C.I. Acid Blue 80 dye according to the LMDR procedure, and rated for uniformity. The uniformity rating iε an excellent 7.8.

Part G - Invention

Nylon 6,6 having an RV of ~50 iε εpun at a melt temperature of 290°C through a εpinneret containing 17 trilobal capillarieε of leg length 0.015" and leg width 0.004". A quench cabinet iε εupplied with a croεε-flow of 20°C quench air at an average velocity of ~127 fpm. The

filaments are converged into yarn at a finish roll applicator just below the quench unit. The yarn is then pasεed through an interfloor tube to an undriven air bearing εeparator roll with a εpeed of 3909 mpm

(withdrawal εpeed) and interlace iε applied. The yarn iε wound on a tube at 3909 mpm and at a tenεion of ~ 0.2 gpd. Thuε, there iε no mechanical draw. The reεult iε a 55 denier trilobal croεε-section feed yarn which haε not been drawn appreciably but, becauεe of the tension generated by the high speed spinning, the yarn is oriented sufficiently in the quench zone to give it an elongation of 85% and a draw tension of 40 g. Thuε, it may be referred to aε a "εpun oriented yarn" (SOY). The feed yarn iε warp drawn on the Barmag STFl draw unit at a draw ratio of 1.316X, a draw temperature of 60°C, an overfeed of 5%, waε relaxed at ambient temperature, and wound into a beam at a speed of 550 mpm. The resulting drawn yarn haε a denier of 43.8 and an elongation of 53.1%.

The drawn yarn is knit into a tricot fabric, dyed with CI. Acid Blue 80 dye according to the LMDR procedure, and rated for uniformity. The LMDR is a superior 7.1. Details of the process and yarn properties are provided in Table 1.

Part H - Invention

Nylon 6,6 having an RV of ~50 is spun at a melt temperature of 290°C through a spinneret containing 17 capillarieε of length 0.022" and diameter 0.015". A quench cabinet iε εupplied with a croεε-flow of 20 ^β C quench air at an average velocity of ~67 fpm. The filamentε are converged into yarn at a finiεh roll applicator just below the quench unit. The yarn iε then paεεed through an interfloor tube to an undriven air bearing εeparator roll with a εpeed of 3954 mpm (withdrawal εpeed) and interlace iε applied. The yarn iε wound on a tube at 3989 mpm and at a tenεion of ~ 0.2 gpd.

Thus the mechanical draw iε insignificant at 1.009X. The result iε a 52 denier feed yarn which haε not been drawn appreciably but, becauεe of the tenεion generated by the high speed spinning, the yarn is oriented εufficiently in the quench zone to give it an elongation of 78% and a draw tension of 40 g. Thus, it may be referred to as a "spun oriented yarn" (SOY).

The feed yarn is warp drawn on the Barmag STFl draw unit at a draw ratio of 1.45X, a draw temperature of 60°C, an overfeed of 6%, waε relaxed at 22°C and wound into a beam at a speed of 550 mpm. The resulting drawn yarn has a denier of 39.6 and an elongation of 30.6%. The drawn yarn iε knit into a tricot fabric, dyed with the CI. Acid Blue 80 dye according to the LMDR procedure, and rated for uniformity. The LMDR iε a εuperior 7.4. Detailε of the procesε and yarn propertieε are provided in Table 1.

Part I -Invention Nylon 6, having an RV of 46 is spun at a melt temperature of 275°C through a spinneret containing 10 capillaries of length 0.010" and diameter 0.020". A quench cabinet iε supplied with a cross-flow of 20°C quench air at an average velocity of ~67 fpm. The filaments are converged into yarn at a metered finish applicator just below the quench unit and the yarn is then paεεed through an interfloor tube and onto a windup where the yarn is wound at a speed of 4200 mpm (withdrawal εpeed) and a tenεion of ~0.2 gpd. The SOY yarn iε not mechanically drawn and paεεeε over no rollε before the wind-up but, becauεe of the tenεion generated by the high εpeed εpinning, the yarn iε oriented εufficiently in the quench zone to give it an elongation of ~67.5% and a draw tenεion of 42.8 g. The yarn haε a denier of 46.

The feed yarn iε warp drawn on the Karl Mayer DSST 50 draw unit at a draw ratio of 1.23, a draw temperature of 80°C, an overfeed of 6.7%, a relaxation

temperature of 120°C, and wound into a beam at a εpeed of 500 mpm. The reεulting drawn yarn had a denier of 40 and an elongation of 42%. _ς The drawn yarn iε knit into a tricot fabric, dyed with CI. Acid Blue 122 dye according to the LMDR procedure, and rated for uniformity. The uniformity rating iε a superior 7.4.

Part J - Invention

10 Nylon 66 having an RV of 65 is prepared as in example F, except that the windup (withdrawal) speed is 5300 mpm. The resulting 13 filament SOY feed yarn for warp-drawing has a denier of 50.5, an elongation of 73.5%, and a draw tension of 63 g.

15 The feed yarn is warp draw on the Barmag STFl draw unit at a draw ratio of 1.15X, a draw temperature of 60°C, an overfeed of 5%, was relaxed at 22°C and was wound into a beam at a speed of 550 mpm. The resulting drawn yarn had a denier of 46.5 and an elongation of 47%.

20 The drawn yarn is knit into a tricot fabric, dyed with C . Acid Blue 80 dye according to the LMDR procedure, and rated for uniformity. The uniformity rating is an excellent 7.6.

Part K - Invention

25

A nylon 66 copolymer, 95 mole % poly(hexamethylene adipamide) and 5 % by weight ε-caproamide units having an RV of 65 is prepared aε in example J. The resulting 13 filament SOY feed yarn for 0 warp-drawing has a denier of 50.0, an elongation of 76.1%, and a draw tenεion of 63 g.

The feed yarn iε warp drawn on the Barmag STFl draw unit at a draw ratio of 1.30X, a draw temperature of 60°C, an overfeed of 5%, waε relaxed at 118 ^β C and waε

35 wound into a beam at a εpeed of 550 mpm. The reεulting drawn yarn had a denier of 39.5 and an elongation of 41.7%.

The drawn yarn iε knit into a tricot fabric.

dyed with CI. Acid Blue 80 dye according to the LMDR procedure, and rated for uniformity. The uniformity rating iε an excellent 7.6.

TABLE I

Comparativc-

EXAMPLE I - Part SPIN SPEED, mpm SPIN DRAW RATIO FEED YARN

NYLON POLYMER TYPE

DENIER

FILAMENTS

RV

ELONGATION, %

(RDR) _F

(RDR) _s

TENACITY, g/d

MODULUS, g/d

DT ₃₃ , g

DT ₃₃ , %CV

DT ₃₃ , g/d

DVA, %CV

USTER, % WARP DRAW CONDITIONS

WD UNIT

WD SPEED, mpm

WD RATIO

WD TEMP °C

OVERFEED, %

HEATER TEMP, °C

RELAX TEMP, °C DRAWN YARN PROPERTIES

DENIER

ELONGATION, %

(RDR) _D ^• TENACITY, g/d

MODULUS, g/d

DVA %CV

USTER, %

BOIL-OFF SHRINK, % LMDR RATING

SUB

69

6/6

SUBSTITUTE SHEET

EXAMPLE II Example II illustrates the effect of warp-drawing conditions on LMDR. The PDY feed yarn described in Example I - Part "F" above iε warp drawn on the Barmag STFl unit at variouε warp draw ratioε and relaxation temperatureε as indicated for items 1-13 in Table II. The resulting beamε are warp knit into a 32 guage tricot fabric, dyed with Cl. Acid Blue 80 dye by the LMDR procedure, and rated for uniformity with the results being shown in Table II.

TABLE IT

Example TT

FEED YARN

DRAWN ITEM NO.

WARP DRAW CONDITIONS

WD SPEED, mpm

WD RATIO

WD TENSION, g

WD TENSION, g/dd*

WD TEMP, °C

OVERFEED, %

HEATER TEMP, ° _C

RELAX TEMP, °C DRAWN YARN PROPERTIES

DENIER

ELONGATION, %

(RDR) _D

TENACITY, g/d

MODULUS, g/d

DVA, %CV

USTER, %

BOIL-OFF SHRINK,% LMDR RATING

FEED YARN

DRAWN ITEM NO.

WARP DRAW CONDITIONS

WD SPEED, mpm

WD RATIO

WD TENSION, g

WD TENSION, g/dd*

WD TEMP, °c

OVERFEED, %

HEATER TEMP, °C

RELAX TEMP, °C DRAWN YARN PROPERTIES

DENIER

ELONGATION, %

RDR _D

TENACITY, g/d

MODULUS, g/d

DVA, %CV

USTER, %

BOIL-OFF SHRINK, % LMDR RATING

SUBSTITUTE SHEET

TABLE IKCONT..

* g/dd = DRAW TENSION(g)/DRAWN DENIER

SUBSTITUTE SHEET

Example III Example III alεo illuεtrateε the effect of warp-drawing conditions on LMDR. The SOY feed yarn described in Example I - Part "G" above iε warp drawn on the Barmag STFl unit at various warp draw ratios and relaxation temperatures as indicated for items 1-6 in Table III. The reεulting beamε are warp knit into a 32 gauge tricot fabric, dyed with CI. Acid Blue 80 dye by the LMDR procedure, and rated for uniformity with the reεultε shown in Table III.

TABLE III

EXAMPLE III

* g/dd = DRAW TENSION(g)/DRAWN DENIER

SUBSTITUTE SHEET

Example IV Example IV also illustrateε the effect of warp-drawing conditionε on LMDR. The SOY feed yarn deεcribed in Example I - Part "H" above iε warp drawn on the Barmag STFl unit at variouε warp draw ratioε and relaxation temperatures aε indicated for itemε 1-14 in Table III. The resulting beams are warp knit into a 32 gauge tricot fabric, dyed with CI. Acid Blue 80 dye by the LMDR procedure, and rated for uniformity with the results should in Table IV.

SUBSTITUTE S

FEED YARN

DRAWN ITEM NO.

WARP DRAW CONDITIONS

WD SPEED, mpm

WD RATIO

WD TENSION, g

WD TENSION, g/dd*

WD TEMP, °C

OVERFEED, %

HEATER TEMP, °C

RELAX TEMP, °C DRAWN YARN PROPERTIES

DENIER

ELONGATION, %

RDR _D

TENACITY, g/d

MODULUS

DVA,%CV

USTER, %

BOIL-OFF SHRINK, % LMDR RATING

* g/dd = DRAW TENSION (g)/DRAWN DENIER

Example V Example V alεo illuεtrateε the effect of warp-drawing conditions on LMDR. The SOY feed yarn described in Example I - Part "J" above is warp drawn on the Barmag STFl unit at various warp draw ratios and relaxation temperatures as indicated for items 1-8 in Table V. The resulting beams are warp knit into a 32 guage tricot fabric, dyed with CI. Acid Blue 80 dye by the LMDR procedure, and rated for uniformity with the results shown in Table V.

* g/dd = DRAW TENSION (g) /DRAWN DENIER

SUBSTITUTE SHEET

Example VI Example VI also illustrateε the effect of warp-drawing conditionε on LMDR. The SOY feed yarn described in Example I - Part "K" above iε warp drawn on the Barmag STFl unit at various warp draw ratios and relaxation temperatures aε indicated for items 1-7 in Table VI. The resulting beams are warp knit into a 32 guage tricot fabric, dyed with C I. Acid Blue 80 dye by the LMDR procedure, and rated for uniformity with the results shown in Table VI.

* g/dd = DRAW TENSION(g)/DRAWN DENIER

SUBSTITUTE SHEET

EXAMPLE VII Example VII illustrates the effect of draw temperature on LMDR. The SOY feed yarn described in Example I - Part "J" above is warp drawn on the Barmag

STFl unit at various warp draw temperatures aε indicated for items 1-8 in Table VII. The reεulting beams are warp knit into a 32 gauge tricot fabric, dyed with CI. Acid Blue 80 dye by the LMDR procedure, and rated for uniformity with the resultε εhown in Table VII. A εharp deterioration in uniformity resultε at a yarn draw temperature of between 156 and 178°C

SUBSTITUTE SHEET

EXAMPLE VIII Example VIII illuεtrates the feasibility of warp drawing yarns containing MPMD. Three SOY feed yarns were used. Item J iε the same yarn as is described in Example I - Part "J". Item L was spun as described in Example I - Part "J", except that it contained 5% Me5-6, and Item M was also spun as deεcribed in Example I - Part "J" except that it contained 20% MPMD. Theεe itemε were drawn on the Barmag STFl unit at the εame draw ratio, but at variouε relaxation temperatureε and wound on a εingle-end winder. The reεulting bobbinε of yarn were knit into Lawεon Tubing and all drawn itemε were dyed in the εame dye bath with CI. Acid Blue 122 uεing the LMDR dye procedure except that only relative dye εhade waε evaluated.

SUBSTITUTE

TABLE VIII CONT

SUBSTITUTE SHEET

EXAMPLE IX Example IX illuεtrateε that when yarnε lack certain physical propertieε which are imparted by drawing, poor fabric uniformity can reεult. Item IX-1 iε a warp drawn "feed" yarn of nylon 66 containing 5% by weight of nylon 6, which iε εimilar to item K in Table I, except that the croεε-εection of the filaments in Item IX-1 is trilobal. Item IX-1 was beamed by normal beaming procedureε, without drawing or heat εetting. Item IX-2 was draw beamed using item IX-1 as the "feed" yarn. Both items were then knit and dyed by εeveral procedureε to analyze fabric uniformity. Procedure "8" iε identical to the LMDR procedure except that the dye iε Pontamine Faεt Turquoiεe 8GL. Procedure "4" iε identical to the LMDR procedure except that the εurfactant Merpol DA iε omitted. Procedureε "4" and "8" are both εtructure εenεitive and procedure "4" iε even more εenεitive to fine εtructure variationε (that iε, to variationε in εtructure openeεε) than the LMDR procedure. Procedure "2" iε a procedure in which the fabric iε dyed for 60 minuteε at 100°C in a bath containing 0.5% CI. Diεperεe Blue 3, which iε a leveling dye. Procedure "2" iε uεed to identify configurational causes of dyed fabric non-unifomrity; that iε, non-uniformitieε which are cauεed by phyεical differenceε in the yarn and not differenceε in dye uptake (that iε, dye rate and/or T _DYE ). From compariεon of the fabric dye ratings (procedures "2", "4" and "8") for Itemε IX-1 (feed, undrawn yarn) and of item IX-2 (warp drawn yarn), εhows that Item IX-2 iε more uniform than the corresponding beamed, undrawn feed yarn Item IX-1. It may be concluded that the non-uniformities in procedures "4" and "8" are caused by the configurational dye non-uniformities (as seen in Procedure "2") super-imposed upon any non-uniformities caused by variations in fiber εtructure. The poorer fabric uniformity of Item IX-1 is attributed, in part, to the lower initial tenεile modulus

(12.2 g/d) verεuε the higher initial moduluε (21.3 g/d) of Item IX-2. Yarns having an initial modulus lesε than about 15 g/d are found to be εuεceptible to being non-uniformly εtretched in normal beaming and knitting leading to poor configurational dyed fabric uniformity. Warp drawing of uniform feed yarnε to increase their initial modulus to values greater than about 15 g/d improves dyed fabric uniformity by reducing the possibility of imparting configurational defects during fabric making. However, drawing said feeds to initial moduli greater than about 15 g/d does not insure LMDR greater than 6 unleεε the feed yarnε are drawn and heat εet according to the invention deεcribed herein.

SUBSTITUTE SHEET

EXAMPLE X In Table X fiber εtructural propertieε are summarized for drawn yarnε formed by dry drawing and dry relaxing variouε εpun feed yarns repreεentative of low oriented yarnε (Figure 17, region I, < 2000 mpm), medium oriented yarns (Figure 17, region II, 2000-4000 mpm), and high oriented yarnε (Figure 17, region III, > 4000 mpm). Feed yarnε used to prepare drawn yarns X-15, 16 and 21 through 24 are repreεentative of region I feed yarnε.

Feed yarnε uεed to prepare drawn yarnε X-2 through 13, 18 and 19 are repreεentative of region II feed yarnε. Feed yarns used to prepare drawn yarns X-26 through 29, 31, 32, and 34 are repreεentative of region III feed yarnε. The apparent pore mobility (APM), derived from amorphous orientation, and the apparent pore volume (APV), derived from wide-angle x-ray were determined for the drawn yarnε prepared with varying draw ratioε (DR), draw temperatureε (T _D , and relaxation temperatureε (T _R ). In Figure 26 the valueε for APM and APV are plotted. Drawn yarnε providing LMDR > 6 and dye tranεition temperatureε (T _DΪE ) leεε than about 65°C are found to have an APM greater than about (5-0.37 x 10- ⁴ APV), preferably greater than about 2, for an APV greater than about 4 x 10 ⁴ cubic angεtromε.

*